Here are my personal favorites and what I think are the best Android titles (games category) that were released in 2012.
I would definitely recommend Jetpack Joyride, Clay Jam, Hill Climb Racing, and Zombie Dash in a heartbeat.
Note that most, if not all, of the games listed above have already received excellent user ratings of at least 4 stars out of 5 on Google's Play Store. Personally, I find Google's user scoring system to be a pretty reliable benchmark for Android apps.
In here, I prefer to rank them in terms of replay value, which is really dependent on the challenges and missions that will make you return daily so as to finish the game.
For other players, it could be about the interesting story arc, solid graphics, or the unobtrusive sound that spells the difference.
Some games got lower marks because they constantly need an internet connection, such as ArelWars2.
Other games were also impossibly difficult to finish if you don't prefer purchasing premium items and in-game goods using real money, such as those offered by Samurai vs. Zombies and Radiant Defense. These apps had very stunning graphics and wonderful gameplay, but I was frustated with the constant string of losses due to lack of 'freemium weapons'.
Here, of course, are screenshots of installed games last year.
Since then, I've added quite a few good ones this 2013, most notably a Japanese title called Battle Cats. I think it's going to be a huge hit this year.
Also worth the look is the Android version of Temple Run 2, which already has an Apple version just last week. We'll see how this year unfolds for amateur & professional Android developers.