There have been a couple of big rumors about PCs that are utterly untrue. I had an old, clunky Windows 95 with no internet that wouldn't even run games made for the system, and so I switched to a Nintendo 64 until we got the brand new sparkly Windows 98 with lightning fast internet which had the best graphics I'd ever seen. So I'd consider myself a half-and-half gamer.
Jump to 2008 and now we have a 3 year old flatscreen Windows XP which still works fine. It plays recent games fairly well, with little to no lag. That brings me to my first PC myth.
PC games lag like crap, making them impossible to play. Untrue. Occasionally you might see a bit of a cut during a gigantic battle onscreen, but it never makes a game unplayable unless you're playing a recent game on a computer that's about five years old which hasn't been updated. Plus, consoles are not immune to lag, either. Even on single-player mode, I've seen Call of Duty lag several times. I can't even count the amount of times my connection has gotten interrupted by the host having a crappy connection, either.
The PC only has three types of games, RTS, TBS and MMORPGers. Also untrue. There are a few good shooter games exclusively for the PC, like FarCry and Crysis. Some people even think they play better on the PC with the mouse than on a console with thumbsticks. Personally, I've never been a fan myself. As a side note, Real Time and Turn Based Strategies will ALWAYS be better on the computer, no matter what you say. C&C: Tiberium was good, but it was better on the PC. If Halo Wars is a success, I'll be the first to bet that it'll be ported to the PC and be better on it.
Those are just a couple of the myths that I've heard far too much of.