A buddy and I were discussing the Wii and how much it costs to get all the little unique controllers. A little later, I coincidentally read an article about how the PS3 is lagging far behind the Wii and XBox in the console market. It spurred me to do a little research to see what the REAL costs of starting up one of these systems are.
For my research, I chose the best version of the console available and assume that you want to play with 4 people total. I chose only the accessories needed to fully play and enjoy any game, not things like a microphone, USB keyboard, etc. Let's also assume you buy two games. I used Amazon.com and EB Games (when Amazon didn't have it listed b/c they are out of stock) to get the prices.
Console (80 GB harddrive): $399.99
Dual-Shock Controller: 3 x $54.99 = $164.97
Games: 2 x $59.99 = 119.98
Console (Elite): $399.99 (Pro - $299.99)
Controller: 3 x $44.99 = $134.97
XBox Live 1 yr: $44.99
Games: 2 x $59.99 = $119.98
Wiimote: 3 x $35.99 = $107.97
Nunchuck: 3 x $17.99 = $53.97
Classic controller: 4 x $19.99 = $79.96
Games: 2 x $49.99 = $99.98
Balance Board: $89.99
Zapper: 4 x $19.99 = $79.96
Wheel: 4 x $9.99 = $39.96
Or with controller accessories: $801.78
It has always been Nintendo's hook to be death-by-accessory. I remember a few Gamecube games that you couldn't 100% complete unless you had a DS. My findings: even though the PS3 console is the most expensive, to get started with everything, it is the cheapest. (A caveat being you go all out on the Wii controller accessories. If not, the Wii is, in fact, the cheapest.)
A few other things to consider: the PS3 is a blu-ray player and a darn good one. Its online gaming is free. It is not fully backwards compatible. The XBox has Netflix streaming. The Wii is Gamecube-compatible but you must have the classic controllers. A lot of cool old-school games are available for sale via download.
For me, the Wii doesn't make sense because it is only fun if you play with someone. I live alone, so no point. I miss some Nintendo titles though. I've just never really been interested in the XBox. Can't really pinpoint why. My draw to the Playstation really has its roots in the Final Fantasy series, but for the PS3, it was definitely the Blu-Ray player that got me.