The war of cross-platform support for popular titles has been ongoing since the emergence of Sony, Microsoft, and Steam. Fans want to play their favorite games on whatever medium they choose, and many say that the Wii's notable lack of smash-hit games like Grand Theft Auto IV and Skyrim are what made players abandon Nintendo's console altogether.
Cross-platform titles may sound like a developer's wet dream in regards to total sales -- but in the end, it's a pipe dream that may never come to fruition. Varying technical specifications, customizable gameplay options, control schemes, and server issues all contribute to the problem. But the Wii decided to forego these issues in favor of playability.
The few cross-platform titles that did come over, like Call of Duty: Black Ops, may not have offered players the chance to play with their 360/PS3-having buddies, but were optimized for the Wii's interface and received critical acclaim.
So is the cross-platform melee the Wii's fault? Absolutely not. Is it a viable reason to completely forsake the Wii as a Nintendo fan with PC buddies? No way.