Wow, Tesco still stock Nintendo stuff? My local one only stocks PS3/360 and The Sims/World of Warcraft.
The bigger a few miles away stocks 3DS too. But that's it. (Don't know if they've ever bothered with Wii U or Vita, but Wii was dumped a while back).
Tesco in particular specialise in buying what sells well in big, and ignoring everything else. This is why it would be an utter travesty if they manage to completely kill off high street competitors.
As for UK/European tastes in gaming. Gamecube outperformed the Xbox pretty much everywhere apart from the UK (where the 360 is now the best selling system this gen). However, Nintendo consoles just don't offer the content that is more popular in Europe.
Nintendo have no major driving titles other than Mario Kart. That instantly is a big turn off to a lot of people who only intend having one console. Add in that FIFA (the most important sport title in most of the world, not just Europe) is generally inferior on Nintendo consoles and Pro Evo doesn't release on Nintendo home consoles (Barring a brief Japan exclusive Flirt of Winning Eleven 6: Final Edition).
And the main problem is Nintendo consoles don't offer the right games to truly succeed in Europe. Where is Mario Smash Football's Wii U version? That would give it a shot in the arm here. The Wii version is still my favourite football game, but it came out in 2007.










