I'm going to pick Battlefield 3. BF3 offers many things. Big maps, many weapons, modes, equipment, jets, helicopters, tanks, etc. Graphics are up to par even when it's console.
Borderlands is a personal favorite. I have it for my PC, but it doesn't have good hardware so it lags a lot. As soon as my family gets a current generation console I'm going to suggest it.
Yeah I have to say Borderlands is a pretty fun game and I can't wait for the second one to come out!