The Wii in my opinion barely beats out Playstation 3, but those two have some really good exclusives that are worth buying a system. The Wii surprised me with the amount of hidden gems that work well on the system, there's a lot of variety of games to be found in the Wii's library, and many of these games can be purchased for relatively cheap prices, and some of these games let you use different options to Wiimote/ or aren't a hinderance with Wiimote. I think part of this has to do with the fact that with the Wii being successful with motion controls and lower development costs allowed companies to create a ton of games for the system, even if there is a bunch of shovelware on the system. It has backwards compatability with Gamecube as well, and getting component output for it is much cheaper than a GC cable, and the Virtual Console offerings are pretty good for the most part. I got it day 1 because of Metal Slug Anthology and I haven't looked back since.
The only problems here are resolution is not good for many games, and you can't import anything since its completely region locked.
The PS3 is pretty close to Wii with variety of games, although I wasn't able to buy one until last year. Many of the exclusives are great indicators of what the system can do, and there are a good amount of games that are better on the PS3 than the X360. Many of the games on this system can be cheap as well, and pretty easy to find still. Being region-free for 99% makes getting imports easy, especially for physical releases in Japan that only got digital releases elsewhere. Online is free as well, native ps1 backwards compatability, as well as ps2 bc compatability( for the first three models), and it can play other media as well( like super audio cds in the first few models). I think the main problem with PS3 is that many of the multiplat titles from some publishers don't run as well as there X360 counterparts.
The X360 has some good exclusives as well. The first few years has a good amount of variety with some exclusives made by Japanese publishers, and in addition has a ton of shmup games, some of which are region free. I didn't get this until 2012, but the library is cool as well. There are a few games that surprised me, like blur, with how fun they were. The main problem I have is that the amount of exclusives stopped around 2009-2010 when Kinect came around, because after that I haven't really seen much on the exclusive side. However, I'd still reccomend the console, just for the exlcusives alone. It does have some bc compatability with original xbox games, but it's defenitely lacking in accuracy and amount of games compared to the other two consoles.
Honestly, I don't think that PS3 support is going to end by 2015, they may extend it another year or two because its still getting some sales and games, compared to the X360 which is just dead at the moment.