What snags your attention with games? What would make you drive to buy it and play it? The graphics? Multiplayer? Art-style? Sound?
Generally, what gets me, is if a game does a little something different out of the norm. Like, if a shooter offers a unique mechanic or two that differentiates from other shooters before it, then I'd be intrigued enough to ponder getting it. I've gotten several games that probably do the same things in their respective genre, but they do it a little differently and that's more than enough to get a pass for me. I rarely act on buying a game based on how many people prop it up as the "best game ever". It's really a matter of opinion and I've honestly played some highly-rated games, only for it to be a disappointment in my perspective and not getting it.
Like Left 4 Dead 2, for example. I've played it, I found it not as cracked up as people have made it. I never bought it but I got it for free when Valve gave it as an X-Mas gift for a day a couple years back. Gameplay is ultimately my deciding factor before almost anything else, with probably art style a close second. Not graphics, just art style, like how creative it looks.