Most people don't buy their systems only for exclusives... if they do, there seems to be something wrong with the hardware if it's only a secondary system and most multiplatform games are bought for the other system. Especially Xbox-gamers had no software droughts in the short lifespan of Microsofts first console thanks to enormous third-party-support.
Just a small comparison how many great games Wii U should get in the rest of its lifetime to be on par with GC, GBA or Xbox: