On "PlayStation 3" for the most part. However, I have a rule- I always buy the same series of a game on the same console. For example, I bought Call of Duty 3 on the "Xbox 360", so I'll buy Call of Duty 5 on the "Xbox  360". Another example- I've played all Resident Evil games on "PlayStation" consoles so naturally, I'm getting Resident Evil 5 on the "Playstation 3".

Now that I've upgraded, I prefer the PC versions. They're cheaper, often have more features, and most importantly, they will be modded soon. Some games go from "meh" to "awesome" with just a few mods (Oblivion, anyone?).

Since I built my new PC, I usually get my multi-plats for that.  PS3 if it is only on consoles.  I'll probably pick up a 360 towards the end of the generation though.

360

yeah when they mod em they rock

 I was about to abandon the Elder Scrolls series until someone sent me to PlanetElderScrolls: since then, those games have absorbed literally hundreds of hours of my life. The same is true for the Total War and Civilization series, and other games here and there. I actually kind of regret discovering mods, since they have a detrimental effect on my social life...

PS3. I figure in 4 years I will still have a PS3. Not sure I will still be playing my 360. Plus, I am 95% sure the PS4 will play PS3 games (probably another CELL architecture), so my library will still work.

The next x-box will almost certainly have to be a different architecture, meaning BC will be suspect.

i think microsoft wont make the same mistake with BC again

 Well, I do :). Good thing we have buying options, so we each can make out own choices :)

360 mostly, though I do have a couple of PS3 multiplatform games such as Burnout and COD4. I couldn't care less about Live and achievements, I just go for whatever version looks and runs the best.