I thought Crackdown was quite good fun, the vehicle and agility upgrades were good, great sound track. There's not much of a story to the game, but it's one of the few 'shallow' games that's fun enough that I play it anyhow.
I really liked Far Cry 2 as well, a beautiful game, and a great setting. I like the little touches too - when you open a weapons crate you actually take the weapon out, it doesn't just jump into your hands. When you're driving around and check your map, it doesn't just pop up, you actually look down onto your lap to look at it as you drive.
Just Cause 2 is a bit similar, but doesn't feel as polished to me. It does have a huge game world, but there isn't an awful lot to do in it. Drive around, destroy stuff. Repeat.
Red Faction Guerrilla is similar in its gameplay, and similar in that the game world is a bit empty. I really liked it, but many others found it a bit dull.
I really like Assassin's Creed 2. It's not one huge free-roaming world, but a few large cities and mid-sized towns, but the world is beautiful, the weapons fun and the collectibles are genuinely interesting.
Oblivion and Fallout 3 are among my favourite games, the amount of items to find, people to meet and quests to complete is staggering. But, IME, they're two of the buggiest games ever made. In both cases the games were fine, but after a long time playing with one character, both games begin to exhibit all kinds of animation freezes and console lock-ups. Considering both games are from the same publisher and (I believe) use a similar game-engine, that's not surprising; even though I own Oblivion on the 360 and Fallout 3 on the PS3.
It's pretty annoying since I'm not close to completing all the quests, but to play them now I have to start all over again as a new character.
Another one that no one has mentioned - The Saboteur. Graphically, it's average at best. The vehicles are awkward to drive, the story is a bit hammy and the main character is as "Oirish" as they come. But it's just great fun to play. Being chased around Paris by Nazi armoured cars and shooting down Zeppelins, then popping around to the local burlesque house for a bit of... what more could you ask for?
