I own every single console besides the PS3 in this 'Seventh Generation' and have heard and read a crapload about them, so now I shall deliver the pros and cons of each and every console including the handhelds. Note that I've only played DS games on a DS lite and PSP games only on the original fat PSP.

XBOX 360

Pros

• Can play DVDs
• A lot of multiplatform games look best on the 360
• Has a stellar online feature
• Can play Music and Videos
• Has a lot of hard-hitting exclusives
• Achievements
• Has a sturdy controller with rumble and a long battery life
• Most packages come with a headset bundled in
• Not too expensive for what you're getting.

Cons

• Xbox Live costs money
• Prone to breaking
• Many of its games are eventually ported onto the PC
• HD DVDs lost
• The majority of the people online are in short: bad people

PS3

Pros

• Free online
• Has the best graphical capabilities of any console
• Six axis and long lived rechargable controller
• Some great exclusive titles
• Music, video and web browser are ALL availlable.
• The 40GB version costs almost exactly the same as a normal blu-ray player
• Blu-Ray Playback
• An awesome deal for what you're getting.

Cons:

• Many games are delayed
• Online isn't as good as the 360's.
• Some multiplatform games don't utilize the hardware and the game has worse graphics or longer loading times.
• Lack of rumble
• Bad use of six-axis.

Nintendo Wii

Pros

• Wii-Mote can be a great way of control
• Free online
• Virtual Console
• All of Nintendo's Core franchises
• Very good for a casual audience
• A lot of games don't have graphical power but great art.
• Most content is Wii-Exclusive
• Cheapest

Cons

• Online is not nearly as good as the other systems with tedius friend codes and lack of voice chat and easily-freezable online.
• Tons of bad gimmicky games
• If you got a gamecube or N64 and didn't completely fall in love with the system, you won't now.
• Least graphical power
• No Video or music play back at all, whatsoever.
• Rumble and mic on the Wii-Mote feel cheap.
• IR sensor isn't all too powerful
• Lacks any AAA RPGs
• Nothing on the Horizon.
• Very low battery life on the Wii-mote.

PSP

Pros

• Tons of media options
• Most graphical power
• A lot of games are handheld versions of big-screen games such as GTA, GoW, Ratchet and Clank, Burnout....the list goes on.
• A bunch of great RPGs
• Has at least one Analog stick
• Widescreen

Cons

• Breaks more often than the DS
• One analog stick can make things awkward
• Not too many genre-defining or completely innovative games.

DS

Pros

• Innovative Touch Screen
• A bunch of great games
• Built-in microphone
• Folding screen
• Diverse selection of titles
• Family fun
• THE WORLD ENDS WITH YOUUUUUUUUUU!!!!!!!!!!!!!

Cons

• A lot of bad games
• No Media options
• Isn't as graphically impressive as the PSP
• Screen scratches, stylus breaks and the frame connecting the two parts of the DS can also break.
• No GBC playback