1: Metallica: Consistently good to this day, even when they switch things up and go tame.(Load and Reload were underrated, fight me.)
Tied with: Slayer: They have a consistently good style that they manage to experiment with here and there, always manage to be over the top and edgy, but somehow manage to work with it IMO.
2. (Pre mid-2000's) Megadeth: Would honestly want to say they almost match the former two above, but everything they've made since the mid 2000's just sounds meh to me. Sometimes it feels like Dave forgets that he also needs to make a song and his political ranting gets too overbearing.
3. Anthrax Not as memorable as the above bands, but still very good. Also love the 90's Groove metal phase they had. Haven't heard any of their post 2000 stuff yet but i'm getting around to it eventually.
4. Post mid 2000's Megadeth: See above.