SWAT 3: Close Quarters Battle (GOTY Edition 2001). Nearly a decade later, and I still hold it up as the best game I've played. It offers everything I could want in a game, and in the debate of quality versus quantity, it holds a perfect middle-ground, offering choice, but without sacrificing quality of game-play. It has an abundance of weaponry, camouflage schemes, effective tactical equipment, commands to get your team mates to do exactly what you want when you want them to, mod support, community in its time...it's been set aside because of it's age today, but I honestly have enjoyed it every time I play it, no matter what I do. It's realistic, as well as fun.
Saints Row 2 (2009) on the other hand, is only about two years old, but it does the same thing--amazing customization, hilariously fun shoot-em-up game-play, all sorts of opportunities for mayhem and destruction, and while mod support is limited, it is mod-capable (I myself am credited with making a mod which lets the player become positively herculean in mass). It's enjoyable, it's entertaining, it's just plain fun. When I need to unwind after a stressful day, or set aside my routine existence and relax--a visit to Stillwater is the first thing on my mind.
But, I only have two hands, and those are two games, so I guess I'll leave them alone together, how's that.