I went through a phase of listening to stuff that never really gelled with me for some weird and wonderful reason, being a bit of a poser in my late teens may be to blame. Anyway, to wrap it all up:
Skyclad, Megadeth and even Ensiferum, who I used to listen, all mostly suck. They have done some ok stuff, but they aren't close to be "good bands".
Operation Mindcrime is a bit of a shit album really, The Warning and Rage For Order are good albums but Mindcrime is just dull, most concept albums are pretty shit generally, even the highly rated rock ones are awfully tedious to listen to, especially Tommy