Louie on 12 January 2009
I also play my Xbox 360 on my HDTV and I didn't notice any issues so far. For me it's rather the opposite: HD games often look sterile to me and I think most Nintendo games have better animations than the average HD game. But I have no problem getting used to HD after playing the Wii for a certain time and vice versa.
On a sidenote I'm gonna scream if someone who obviously never owned a Wii comes in and claims "Wii graphics look terrible on my HDTV!". 
