To be honest it depends what you yourself are looking for in a Games Console.
Nintendo DS - This is a good handheld with hundreds of games available but graphics are obviously limited and unless you use a flashcard to be able to play music, internet and movies you have just a basic gaming machine. This console I think is more towards the younger player.
Sony PSP - A very good handheld with excellent graphics and unlike the competition can play movies without having to add anything to it. Internet browsing built in is also a nice feature. Nice wide range of games and films are also available for the PSP.
Nintendo Wii - Well everyone knows its one of the most popular consoles ever and they estimate that out of all console owners in the world the Wii will be owned by over 50% of them. The console is probably the first family friendly one where everyone can get involved. A wide selection of games and so many addons make this very attractive, only downside is the graphics, they are not the best. While a winner with thousands for its playability its not classed as a hardcore gamers machine.
Xbox360 -Usually playing second fiddle to the PS3 the Xbox sales have recently shot through the roof, 3 weeks on the trot its outsold the PS3 in Japan and the graphics and playing are awesome. Loads of games and online play is first class. Loses out on a couple of things to the PS3 but with the new lower price announced only 2 weeks ago it is definitely worth looking at just for that.
Sony PS3 - Well it is the Daddy. Amazing graphics does make this the winner and with the bonus of bluray it does give it the edge over the Xbox. Downside is the price, still very expensive and some parts of the world the games are very overpriced but if you have the cash and are a hardcore gamer you cant go wrong with the PS3.