Riot is one of my all-time favourite bands so I gotta weigh in. As DMR said, Thundersteel and Privilege of Power are your albums. Have you checked out the really early stuff with Guy Speranza on vocals though? Those two aforementioned albums were my intro to Riot (and I love them dearly) but the late 70's/early 80's material just might be my favourites. If you're into old Judas Priest and mid-era Thin Lizzy then chances are, you'll dig albums like Narita and Fire Down Under too. It's got a seriously dirty, rawk-with-utmost-hardness attitude and they really pushed the envelope in terms of metal riffing and speed in those two albums, especially Fire Down Under. Plus, they're catchy as all the deadly sins and that singer has a great storytelling vibe in his delivery. Worth a look if you're into Lizzy and ancient Priest. Old Saxon too, for that matter.
Let's make it simple; check out the first two tracks plus "Run For Your Life" and you'll probably know if it's your thing or not.