On the chess arguement, fritz 3D was a quad xeon galatin MP @ 2.8Ghz, with 4GB memory. That's hardly a supercomputer, it would cost about 12 grand to builld and maintain for 3 years. At this point, if Blue Gene, when it is completed of course, where faced against Gary Kasporov, he would lose, hands down. So what if the computers know what he has done in the past, Kasporov at this point makes up a new move to screw with the computer, and it is more than a decent strategy. Deep Blue is still 6 years old, remember that, and much has been learned on both sides. Mark my words though, there will come a day when computers consistently beat men, and it's not that far away.
I really don't like playing against AI though. AI relies upon 2 tactics, holding the strong attack point, i.e. holding a room in a FPS or a field, or by relying on a specific fault and power only, like in a game like Diablo where most enemies have an immunity to something and a strength in the same field.
When you play a game online, it is ALWAYS much harder to defeat everything. Have you ever tried to play a FPS online compared to even the most attuned AI? The difference is that AI relies on an algorythm to know where you are, there is nothing random about it. 9/10 times I can do the same thing to a AI character and he will respond the same way. Humans will be random quite often. Humans make mistakes, and they are far more random, this is less luck, more skill.
For instance in a FPS, playing single player, you can basically pick off an entire enemy team, and they would barely take notice, even on the hardest difficulties, in an online game, you probablly wouldn't make it past 1 before you were being shot at.
They are two very different worlds, and until there is some kind of algorythm to make AI keep up.