I really dig procedurally generated content. PGC, more or less, makes a game endless and you get wayyyyyyy more replayability (is that a word?) out of it.

Also, user created content (ala littleBigPlanet) is great. DLC is all well and good, although I agree with Lunar - it should be free.

Really, what I'm looking forward to, are games where almost everything is procedurally generated - from levels, to characters, to storylines, to enemies, to weapons, to music and maybe, eventually, even gameplay mechanics (think ROM CHECK FAIL, but actually PCG and with more mechanics that actually make sense within a game world).