I'm going to have to say that I disagree with Garchomp going to S-Rank. I've used Garchomp in the past, and frankly, Garchomp is just a bit lacking, I think. True, it has fantastic stats all across the board, with great attack, solid bulk, and good speed. The problem I have with Garchomp is that it's just... bland, in a way. It's almost perfectly balanced, which is something of a problem in this Dragon infested metagame. A good portion of the sets Garchomp can run are done better by other dragons. Choice Band? Haxorus and Kyurem-B have more attack, letting them leave much more of a dent, which is the whole purpose of a Choice Band set. Choice Scarf? Lati@s is faster and has Trick to cripple things with, and Salamence has that amazing Moxie to get an easy sweep. Swords Dance? Thats something I'll have to hand to Garchomp, since not a lot of Dragons actually get that, but it misses out on Dragon Dance and the speed boost it grants, making it easy to revenge kill. It's ability to lay Stealth Rock is certainly unique for a dragon, but I don't think that that really pushes him up to S-Rank.
Overall, I just feel that Garchomp is a jack of all trades, but a master of none. Most of what it can do can be done better by other dragons, making it somewhat outclassed to a degree. What it's good for is being a very balanced dragon; if you don't need the specialization that the other dragons provide, Garchomp is a good choice. However, I just don't think that something like that is really worthy of S-Rank.