The Arduino won? I didn't even know there was a contest!
There are lots of microcontrollers and boards out there: Basic Stamps, PICs, 68HC11s, Parallax Propellors. You can get some for as little as $3 each. There's probably more stuff out there for Basic Stamps than for the Arduino. There's definitely more PIC related stuff.
Basic stamps and PICs used to get a lot of usage in hobbyist projects, but that has changed in the last couple of years. First it started shifting from PIC to Atmel, and then to the (Atmel based) Arduino. It's been a while since I've seen a new project that someone had chosen PIC for.
IMHO the move to Atmle may have been partially due to the PICs super annoying architecture (bank switching for every other operation, for starters). The Arduino of course has a big advantage for people who don't want (or can't) design their own PCBs.
If look at Projects on Make, or elsewhere online, you'll see Arduino being used in the majority of the newer projects.