Vegas 1 vs. Vegas 2
Perhaps the afterglow left by the new play style gave me better impressions of the first game's story, or maybe it was the sense of mystery, discovery, and the cliffhanger ending of the original that made it feel so much more fresh than the sequel's continuation. In Vegas 2, you know you're after Gabe Nowak, and the story is mainly about him. There's no sense of discovery, uncertainty, or revelation. You just have to find him, hear out his motives (no really, you have to sit through his whining), and stop him. In terms of story, Vegas 1 wins. I have to also give atmosphere and pacing to Vegas 1 for being mostly at night and using more colors and lighting effects to really bring life to the game world of Sin City.
However, the multiplayer scene is more or less the opposite. Vegas 1 does feature four-player campaign co-op, which is a definite win over the two-player limit for the sequel's co-op campaign, since the AI guys have to tag along the entire time in Vegas 2, something else I saw as a weakness of the sequel in general. However, despite having basically the same play modes for the rest of the multiplayer (co-op and competitive), the experience and leveling system for V2 coupled with allowing respawns and the ability to carry two primary weapons instead of only one (as in V1) makes V2's multiplayer infinitely more enjoyable and dynamic. V1's co-op terrorist hunts gave each player only one life, so even one mistake can be the end of the match for you. If this happens early in the match, it can lead to a lot of boredom. V2 allows up to four respawns depending on difficulty, though at least one other team member has to be alive for you to be allowed to spawn. If everyone falls close to the same time, you're all out. Unless you play recklessly, odds are you'll finish together or die together, but not have the downtime V1's multiplayer exhibits. Taking chances and failing doesn't punish you as hard if you have a few respawns in your pocket.
One other slight Achilles' Heel for V2's multiplayer is that, instead of loading to a lobby where you can send invites and chat pre-match (like it is in virtually every other title, including V1), it immediately throws you into a match, forcing you to either die to be taken back to the lobby, or try to send invites while dodging enemy fire. Not a huge deal, but it could easily have been avoided. Also, V1 always offers a minimap on-screen, something you need to hold a button down to see on PC. In the end, despite minor hiccups, V2's multiplayer takes the trophy between the two titles for its depth and added flexibility.