Vulgar Display of Power is very close to Cowboys From Hell, but I got to give the vote to Vulgar. Absolutely perfect 1-2 punch of albums, great song-writing, good lyrics (complete with a couple of dodgy moments, which I find just add to the character of the album!), and great energy. I think that part makes them really stand out to me is the fact they sound like an actual band, it sounds like they're actually jamming, in your stereo. Far Beyond Driven, Great Southern Trendkill and Power Metal are right behind them too. Reinventing The Steel is next in line, then the other three.
Yesterday don't mean SHIT.