Now this is the hard decision to make. Both these two machines can be considered as consoles http://www.kidsgames.org/ aimed at the "hardcore gamers". This involves action packed games such as Splinter Cell, first person shooter games like Call of Duty, and even Role-Playing games like Final Fantasy 13.
These are games that involve more time, attention, and concentration, so they are thusly meant for those who are more "hardcore." Generally speaking, the graphics for these games are very detailed and realistic, which adds to the dimensions of the games, as opposed to the Wii games, which are generally more cartoonish.
More recently, many gaming companies have chosen to release their games simultaneously for both the Playstation 3 and the Xbox 360, making the decision between the two consoles a rather tough http://www.crazymonkeygames.com/ one.
Below I will I thought about this attempt to highlight the specific points about each console which may be factors in helping decide which of the two consoles is right for you.