I agree that Wii's are basically impossible to get this time of year, i waited in line today for kmarts thanksgiving sale, and was there at 4 am, they opened at 7 and was one of the last people to get one.
Ive played all three systems and what I think is this:
Wii- It's fun to play with groups of people. As far as content goes for other games, I dont know yet, Ive only played sports and guitar hero.
Xbox 360- most my serious gamer friends have this, and after playing it I understand why. Also at my age (19) xbox 360 seems to have more of a lineup of games I like, and good online play brings a whole new element to the systems, and i think the 360 does that best
PS3- pretty expensive, the selection of games is allright, but I wasnt impressed with online features compared to the xbox360, which is what I like to do mainly when playing a system.
Overall i would have to say if your going for good online play and play alot the 360, but if you only play games every so often out of boredom or with a group of friends the Wii.