I believe that when buying a system it is important to consider a few things first and foremost does it have the quality of games I enjoy. If yes continue then you consider the likelihood of more games you will enjoy emerging in the future. If yes continue, lastly you look at what else the system can be used for since it is important to get the most out of your money.
The winner is PS3!
Why the system really came into its own in the last year and a half and 2010 looks even better for great PS3 exclusives. Furthermore, the system seems to have barely scratched the surface of its potential according to many developers. Lastly, the inclusion of a blu ray player and free online access puts the system over the top.
Will Natal change things?
Will everything go digital?
Will developers start using the PS3 as the lead console in development?
Those are important questions to consider but as of right now I would pick the PS3.