I used to despise GTA. Because, at one point (i.e. San Andreas) it was one of the most over rated game series ever produced. When GTA IV was about to be released, I sighed to myself. Not again. But I'm not a prejudiced person. When my brother bought the game, I played it and found I really liked it. It was so much better than al lthe other GTA games. It's one of my favourite games of this generation, too.
Now I'm Irish, so I don't "get" American Football. I played the Wii version of Madden and it was good fun. Confused the hell out of me, but I find sports games where you don't know what you're doing to be the most fun. Me and my brother, running around on the field and using weird runs and strategies that we didn't quite understand. Fun stuff.
But GTA IV is just a brilliant fun. It's not difficult for a game to be fun. But it takes a game on a whole new level to make you emotionally invested in it's characters and stories. But GTA does it very well. Especially with that ending... *sniff*...