I had a PSX and PS2 and I will get a PS3. I stay loyal to Sony, they've been good to me so far, I have no complaints with my systems that's why I chose them.
What has Sony done lately?
PS1 was very good, and they had some great new series come out like Spyro and Crash (now available on all consoles).
PS2 was decent in the beginning but is the worst of the current-gen consoles as it has basically no advantages over the other ones.
Disadvantages:
Xbox has better online gameplay(Live!).
Gamecube and Xbox both have faster load times.
Xbox has better graphics and some Gamecube stuff does as well(I was surprised at the latter, but GC seems to be pretty equal graphics wise for most games despite the fact it has less raw power)
You cannot import music like Xbox can.
Advantages:
Can play DVD's without any add-ons.
A few exclusive titles not available on others, but this lessens everyday.
Fantavision and Amplitude.
I am no way biased towards any console, I just call things for what they are and Sony has gone down the tubes. They were great when they started, but did they just get lucky?
What has Sony done lately? Nothing. They've been too focused on entering the portable gaming which has not been as successful as it should have been because they do not make very many good games anymore, which shows heavily in their software sales lagging lately.
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What has Microsoft done lately?(Personally I do not like Microsoft at all... so I have no idea why I support them here I just feel it is the most solid system)
Signed on game developer Rare to make classics like PDZero, Banjo-Kazooie and a few others for the XBOX.
Best Online gaming, Xbox Live Arcade.
Best controller thus far, both the one for the original xbox and the 360.
360 Shortages (

)
Continually improving the quality/selection of their games.
Creating new original titles
and more tricks up there sleeve that are likely going to stay hidden until shortly before the PS3 is launched.
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What has Sony done lately?
No news of the PS3.
Quality of games dropping on the PS2.
No new innovations yet... just "making the graphics better".
Delayed launch.
Launch shortages like Xbox is predicted...
Pathetic Portable. UMD's...yikes.
Price...(TBA)...but Blu-Ray MAY be a benefit.
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What has Nintendo done lately?(I am a fanboy... but the NGC didnt sell to me at first but the more I play it at friends houses the more I realize that the games are great, and I would buy one....but will wait until the Revo comes out and get NGC games then)
For current-gen Nintendo hasnt done too much, although news is slowly leaking about their next-gen console.
Low price, maximizing the use of what you have in your system meaning it runs more efficiently.
Nintendo has new innovations and promises new titles on the Rev. and likely no shortages, and looks to have a very bright future with the new console.