I'm kind of surprised that the Japanese companies aren't rallying behind the Wii U, but I'm not surprised by Western Devs' support for the thing so far. The Wii U launch was packed w/ Western Developed 3rd party games like ZombiU; Black Ops 2; Assassin's Creed 3; etc. and has anyone gotten the impression that they've sold well? The most damning thing I've heard is that anecdotal report I heard on a podcast (Giant Bomb, I think) of 400K+ online players each on Black Ops 2 PS3 & 360, 400 total on Wii U.
3rd parties are still burned on Nintendo from the Wii years, and for better or worse (justified or not) Nintendo seems to have burned their bridges with EA. Until the Wii U starts selling consoles, I can understand the Western Devs not wanting to waste their time and expensive manpower on Wii U ports they have good reason to think won't sell well. They also could flat out not have gotten final dev kits until shortly before the Wii U launch, so they're slow to get set-up for Wii U development.
Like it or not, the Wii U's underwhelming launch numbers and total lack of hype aren't helping Nintendo's case with 3rd parties right now. And unless Nintendo can get a game out there soon that really gets people excited to play Wii U, I don't see their situation improving.
Is it right that 3rd parties are giving Nintendo the cold shoulder despite the Wii U now being on-par with the other 6-7 year old consoles? Probably not, and there's certainly a business opportunity to be had from being the biggest fish in a tiny pond. However, this is likely Nintendo reaping what they had sewn with the Wii years.