Metal Gear Solid: Peace Walker
I'm not all that super-psyched for Revengeance because I personally think it doesn't look or feel very MGS (it's more of a spin-off), but I can see myself trying it eventually.

Anyway, Peace Walker is absolutely the best Meat Gear Solid game and I got to play a little bit of it on PSP because I refused to play the game solo. I bought the HD Edition on PS3 and it's incredibly fantastic. I wanted to play it before any more Metal Gear games came out so I can remain in Kojima's strange and twisted loop. I definitely had to make sure I played Peace Walker before more details on Ground Zeroes came out.

If anyone has the game (on PS3), I'd love to play some co-op; it's always more fun playing with familiars.
I have to say, Peace Walker is quite fantastic, beat it on PSP, might have to pick it up for PS3 since my PSP no longer functions properly.
I have it on ps3 and psp and it is great.
It costs $19.99 to buy standalone via the PS Store. I thought that's a very fair price for this game, it's really packed with content. It also plays much better on a console since you have the right stick as your camera instead of the four face buttons. 1080p and 60fps also help!
I played it on PS3 so my opinion is skewed in that it is very much a mobile game and not much of a console game.

That's not to say its not awesome but the way gameplay is segmented gets to be a little grating when you're on a couch trying to play the damn thing for an entire afternoon as opposed to on a bus and only trying to play for 10 minutes.

Also the CQC in this game looks great. They really nailed it without having it be a mess of held buttons and directions like in MGS4.

I don't have it any more but I don't know I might rent it again some other time.