Really? I remember trying to beat the single player campaign on the PC version several years back but IMO, it was pretty boring so I quit and went back to playing the online MP. :x (And I still find CoD campaigns to be pretty entertaining, sure the enemies tend to spam 9,001 grenades at you sometimes and I think that infinite respawning enemies are still in? Regardless, they'll keep you entertained for 6-7 hours. I also beat them all on Veteran difficulty.)
Eh, I still find killing Russians to be fun. Nukes/missiles also have to be involved as well. I kinda wish that Activision didn't totally **** over/ruin Infinity Ward. The single player campaign would've been different and yeah. (Don't wanna spoil MW3's story for you if you haven't beaten it yet.)
And you're sold on the Wii U? I'm not yet. I plan on waiting 2-3 years for next gen.