PS3 is the best value obviously. You get DVD/Blu-ray player, built in wifi and the online is free. For 360 wifi is extra and online costs money. The wii has no DVD player. So its pretty clear VALUE wise the PS3 is the best.
The 360 has been better value for me, cos it's the console I use the most by far. You can't just look at hardware spec sheets. It's how you end up using the consoles that matters. The 360 outperforms the PS3 in most cross-platform games and without silly forced installs and other annoyances, and the online service is much better and is therefore more than worth the £26 I've just paid to renew my 12 month subscription. I don't use the Blu-Ray player in my PS3 (other than to play games obviously) or the wireless, so that makes no difference to me. It's only used to play exclusives (at the moment at least), so it's essentially just the same as the 360 but with a smaller games catalogue and worse online (although it's free). As for my Wii, well that poor bugger hasn't been turned on for a long time and if I could go back in time, I'd keep the £180 I spent on it in my wallet.