I don't know yet, whichever system has the highest volume of games available (or will be released shortly) which I am interested in at the time the price of the system is low enough for me to bite.
In the generation before this last one I had an N64, a PSone, and a dreamcast. When the time came to decide between the PS2, GCN, and Xbox I just did the simple anaysis above, and the PS2 had not only a higher amount of games, a greater variety of games, and lower overall price of games than the other 2 systems at the time, so I picked PS2. If this generation the X360 or the Rev have a better lineup of games at the time of the 1st or 2nd price drop, I will bite on that instead of the PS3.