Hmmm good topic!!!
Kinda hard to answer too because some of the places that may be great to visit are only great to be there in small doses because they're not liveable, and some of the most liveable places may not be the most interesting to visit.
Reading above I agree with alot of the comments that have been made about places I've also been to. I'll just write up a bit about some of the places I've been that I have comments about
London, England: Interesting place with lots of history but extremely unliveable, no way I could live there. Spent about 2 weeks there all up, and was relieved to be out of there because it's a pretty claustrophobic city. Too crowded, too overpriced, and feels really cramped. You also don't get the feeling of everything being so easily available whenever you want as you do back here.
Birmingham, England: Agree 100% with Blitzy. Dismal, industrial, boring, lifeless city. I really just went to see Tigertailz, otherwise it would've been a complete waste of time.
Nottingham, England: Had a blast here because I went for Firefest, and the Pit & Pendulum is an AWESOME pub! Seemed like quite a quaint little town but don't know if there would be much else to do there.
Torquay, England: This was a really really nice seaside town. I went here for the Fawlty Towers factor really haha, but it was the nicest place in England I went to by far. Really nice little getaway destination! Great home made ciders down here too!! The people were really friendly too and I loved the accents down there, my favourite English accent!
Amsterdam, Holland: BEAUTIFUL city by day, awesome architecture, beautiful canals... Red light district is heaps of fun by night! I also got mugged twice and got out of it pretty lightly so it was worth it for the story! A highlight of the trip!! Haha.
Copenhagen, Denmark: Another very beautiful city but seemed pretty boring. Not a whole lot to do there but it does seem like a pretty comfortable place to live.
Germany: Noticed a big difference between the northern & southern parts. Hamburg & Berlin were two of the most similar cities to Melbourne that I've been to. Pretty diverse cities with an artistic & alternative edge with people who are passionate about what they are into and really embrace everything. Down in Bavaria was way more traditional but I
loved the character of it, and they love their beer! Munich was pretty good, but Nuremberg I really loved - possibly my favourite city I went to in Europe. It was a good blend of being a quaint looking European city with good architecture (and a walled city centre) but still had enough diversity and stuff to do to be liveable as well as just being a pretty or interesting place to visit. Plus I have great memories of seeing the mighty Pretty Maids there!!
Italy: Only went to the north. A great place to visit and a beautiful country, I would visit there again in a heartbeat and want to see alot more. However I could never live there. Stunning cities - especially Florence & Venice - but just not much to do to the point of it even being hard to find bars to go to at night. As a destination though for a holiday, great country with so much culture & history and a beautiful place. Plus I love Italian movies so I felt like I was in a giallo film the whole time hehe.
Paris, France: Only had a day there so can't form a proper opinion but that day, the first word that comes to mind is overrated.
Los Angeles, USA: Like London, I had a couple of solid weeks here based in one place so was able to get a better sense of settling in to get a better feel for how the place would be to live. But unlike London, which I found entirely unliveable, by the time I had to come home from LA I felt like I had settled in completely and it was almost weird leaving, so I found it a really liveable city. I think just how similar the USA is to Australia, both countries having that same feeling of being able to get whatever you want whenever you want in any variety that you become accumstomed to makes it liveable. Plus, there is so much diversity in the city where different neighbourhoods just feel so different from each other, from Beverly Hills to Compton, Hollywood to the Valley suburbs, the south bay suburbs right next to South Central LA neighbourhoods etc, so much contrast. Like Blitzy said though, the problem with the USA is the people. Arrogant.
San Diego, USA: Beautiful city, also very liveable. But nowhere near as much interesting contrast as LA. Would be a great city to retire in if you were American though.
Las Vegas, USA: AWESOME place for a weekend but gets tiresome after a few days as it's nothing but casinos really. Doesn't feel like a real city, feels more like a city-wide amusement park but it's great that you can drink on the street!
Tijuana, Mexico: By far the dodgiest place I've been. Never been offered machine guns & illegal weapons multiple times in one afternoon before - along with a whole lot more dodgy offers. Was a good experience though!
Whitsundaes: Best beaches & clearest water in the world, with perfect weather. Beautiful holiday destination!
Sydney: I noticed a few people putting this as the worst destination. I just got back from there last week again and to be honest, I hate the place. The harbour is really nice, the weather is good, but the city really lacks character. Bondi Beach is also the most overrated beach in Australia, the epitome of the type of beach that made me hate beaches when I was younger actually (I quite like the beach now but Bondi is horrible). The city just has nowhere near the interesting bars, shopping, nightlife, restaurants, cafes etc that characterizes Melbourne - to the point where even in parts of downtown Sydney itself, we walked around for ages just trying to find a relaxed looking cafe to eat, and there seemed to be no middle ground between posh looking places that looked expensive or having to settle for a Gloria Jeans or something! And with the exception of Newtown and the Cross area, it also just doesn't really have range of interesting different inner-city neighbourhoods that offer their own unique character. That said though, I guess being a big city in Australia I'd rather still live there than most places overseas, but I wouldn't regard it as a desirable holiday destination for myself as it just doesn't offer anything of interest to me.
I agree with what Tim said too about travelling overseas making you realise how good we have it here, and that we should be pretty proud that we live in this country
I'm biased as it's my hometown but I think there's a good reason Melbourne has repeatedly tied as the world's most liveable city. I'm yet to visit somewhere that I would rather live than Melbourne and I'm always happy to come home to it. It's a perfectly balanced city, where other cities may be
unreal for a certain aspect but have other big detractions, Melbourne is pretty much just good for everything. It's diverse & multicultural, big enough that it offers everything you need yet not overcrowded or too busy and doesn't have major crime problems, the city is just chock full of interesting bars & cafes & shops hidden away down alleys & laneways, and all the inner suburbs offer their own unique flavour. From even just walking down Chapel St you see the huge contrast between South Yarra & Windsor, to the Italian cafe culture of Carlton to the vegan & artist culture of Fitzroy & Collingwood to cheap Vietnamese dining in North Richmond to St Kilda's stark contrast of yuppies in glitzy bayside cafes & new high rise apartments right amongst its seedy underbelly of junkies, homeless, cheap rooming houses & illegal street prostitution. The weather could definitely be better here though!! I find it hard to see what Melbourne would offer as a holiday destination though as it's too familiar to me and doesn't really have the notable "sights" that other destinations have.
Destinations I most want to go?
Well, USA is next on my list of places to go back to. Like Mark said, I want to get a car and just drive state to state and see it all. I'm much less interested in New York as I would've been before it got cleaned up alot in the '90s. I really want to do Arizona, Texas then the deep south, and then head up to the midwest and I'm fascinated by all the crumbling cities like Dayton, St Louis & especially Detroit that just lost all their industry and have halved their populations and have really become half-empty shells of cities overrun with crime. Also, I have to go over during NBA season so I can catch some live games!!