Its not neccessarily the games that make online gaming better...
Its the fact that you can game with good people. I have been an Xbox Live subscriber since March 9th 2002 (Coming up on my....4th renewal). Wow, that seems so much longer.
What has made me stay? The community! You meet good people to play games with. No screamers, no cheaters...just gaming, and fun at that.
So, my word of advice? Find a good community to play with, and stay with them.