Err, Gamespot, 6.0?? Really?? Did you really bother playing the game?
In a nutshell, you pick one of many Champions, team up 5v5 (Summoner's Rift) or 3v3 (Twisted Treeline), and level up while attempting to overpower the enemy team and destroy their base before they destroy yours. Of course, there is the brand new Dominion Mode, which I have yet to try out properly, but the one game I played was so much fun. Then there is the classic game mode, with normal and ranked games.
To keep things fresh, there are a few champions available to all, that keep rotating each week. So you basically try out every champion in the game after awhile. Not to mention, a new champion is brought in to compete in the Fields of Justice almost every 2 weeks. Hence, a lot of new stuff added which keeps things fresh, fun and challenging.
Losing long fought games can be as thrilling as winning them. Sometimes single handedly carrying your team seems highly satisfying, and gives you the bragging rights.
Best part of all? THE GAME IS FREE!!!!!!!!!