I never know how long to make these lists (not that I do this often  

  ), but how do you know when an album is one of your favourites? I thought about it, and its probably the ones you have listened to the most in your adult life. The ones you always go back to, regardless of how many times you've heard them, often sacrifising listening to new music or stuff you have you know is really good but haven't given the time of day (yet) because you were listening to these albums. It should therefore be a very personal list, a soundtrack to your life, if you will, not just a list full of "classics" or cool underground shit. Because of this, the dilemma is what to leave off it.
Anyway these are my "favourites":
DJ Shadow - Endtroducing
Wu-Tang - 36 Chambers
UB40 - Signing Off
Aphex Twin - I Care Because You Do
Bonobo - Dial "M" For Monkey
Spacemonkeyz vs Gorillaz - Laika Come Home
Burial - Burial
Nas - Illmatic
Royksopp - Melody AM
Beastie Boys - Check Your Head
A Tribe Called Quest - Midnight Marauders
Kings Of Leon - Youth & Young Manhood
Fugees - The Score
Enigma - MCMXC a.D.
Modeselektor - Hello Mom!
Leftfield - Leftism
Portishead - Dummy
Massive Attack - Blue Lines
Richard Dorfmeister - A Different Drummer Selection
Kasabian - Kasabian