The Saboteur
Most GTA clones stick to imitating the gritty modern-crime formula, with some floaty aiming and driving controls tacked on; "not as good," in so many words. But, as they showed in Mercenaries, Pandemic has had a knack for making an open-world havoc game thematically different enough that it feels unique - special, even. The Saboteur does this in two ways.
The first is killin' Nazis. It may sound hackneyed, but through the city's oppressed color palette, asshole Nazi NPC behavior, and (somewhat spotty) story scenes, The Saboteur does a great job of vilifying its villains. More so than receiving upgrade points or advancing the plot, killing those fuckers feels like a genuine reward in and of itself.
The second is tits.
The Saboteur is a rare case where, in spite of some jarring voice-over accents and jerky character animations, the game world feels highly immersive - because I want to play in it. It preys on my knowledge of historical events, my desire to see the Nazis defeated, and my desire to help Sean Devlin get his revenge. It's a compelling package.
As for the gameplay, it's very workable, although I don't know that I've been blown away (no pun intended) by anything so far. Naturally, the driving controls are a little floaty; aiming is okay, though. There's some Assassin's Creed in here, too, as Sean can climb to the rooftops - but once he's up there, rather than parkour around the city, he tends to just blow shit up.
There are a jillion non-linear objectives scattered around Paris, from destructible Nazi structures, to observation points, to car collecting, not to mention unlockable "perks" from completing particular challenges. For instance, killing a bunch of Nazis with grenades got me a bigger bomb bag. Though I have yet to dive in too deeply, all those little objective blips on my map are very enticing.
Progress: Act 1