Topic: X360, easily.
Side Topic:
GTA4 might sell well. On the plus side, it's an established name brand. On the minus side, it may have worn out its welcome with GTA3, Vice City, San Andreas AND Liberty City Stories. LCS didn't sell as well.
Assuming demand hasn't died down, GTA4 will easily outsell GTA3.
For comparison:
PS2
US
GTA3 was released on 10/22/01.
4.869 million PS2s in the US.
Others
GTA3 was released on 10/26/01.
3.875 million PS2s in Europe.
If GTA4 were to be released right now in US and Europe:
8.8 million X360s US
4.34 million X360s Others
2.61 million PS3s US
2.30 million PS3s Others
GTA4 has a larger user base to sell to compared to GTA3. 20 million LTD may not be too far off.
There is no such thing as a console war. This is the first step to game design.
