I'm gonna omit compilation albums and live albums from my list. Just twenty essential original studio rock albums that kick ass, not in any specific order.
1. Led Zeppelin IV
2. Physical Graffiti - Led Zeppelin
3. Abbey Road - The Beatles
4. The Beatles (White Album)
5. Black Sabbath (debut)
6. Paranoid - Black Sabbath
7. Are You Experienced - Jimi Hendrix
8. The Doors (debut)
9. L.A. Woman - The Doors
10. Who's Next - The Who
11. The Who Sell Out
12. Who Are You - The Who
13. Van Halen (debut)
14. Women And Children First - Van Halen
15. Dark Side Of The Moon - Pink Floyd
16. The Wall - Pink Floyd
17. Metallica (Black Album)
18. Sticky Fingers - Rolling Stones
19. Some Girls - Rolling Stones
20. Back In Black - AC/DC
There are many great ones that could be added. That list only scratches the surface. I could list every Ozzy-era Sabbath album, every Led Zeppelin album and most Beatles albums. Guns n' Roses, Slayer, Beach Boys, Alice Cooper, Aerosmith, Frank Zappa, Stevie Ray Vaughan, and many others deserve to be on the list too!