It's going to be almost solely dictated by what you want to play on the console. For example, I bought my Wii U as a local multiplayer machine, so games like Splatoon (which is basically useless on a local multiplayer level) and Bayonetta 2 (which is focused primarily on solo play). Still, there are several games to mention:
Super Mario Maker: Sadly, it's single-player only. This has me uncertain if I'll get it, because I got my Wii U to play with others. Still, it's a powerful level creation game with online sharing of courses, meaning an endless supply of levels.
Yoshi's Woolly World: Like Tropical Freeze, it's going to be limited to two-player co-op. However, it's a great-looking game and is supposed to be a reasonably tough game to 100%. Also, it has amiibo support (only for visual changes to Yoshi), if they interest you.
Super Smash Bros.: Get it, I don't think I have to explain myself. It's great for local multiplayer, it's got some online play, it's just a great game. Plus, they're given it decent DLC and support.
Mario Party 10: Kill it with fire and run away screaming. They've neutered this franchise, and I'm extremely disappointed in it. I could go into great detail about everything they've ruined, but it'd be a long rant. Just go read online, and you'll see that there's a reason it's the rare Nintendo-made title with weak review scores.
Mario Tennis Ultra Smash: It's coming out, and if you like Mario Tennis games of the past, you should be good for this one as well.
New Super Mario Bros. U: I'll just include Super Luigi U here as well. If you like traditional Mario platformers and want a couple to play alone or with others, you've got it. The only complaint is that playing in local co-op with the tablet means you're a support person (building extra platforms for people). It makes the game WAY too easy to beat, but without it, you'll get a typical experience.
Bayonetta 2: As was said, reviewed well, but I haven't played it. I would if my Wii U were at my house, but it's not, and I've got a lot of Xbox One games to play in the near-future.
Zelda Wind Waker HD: I didn't care for it, but if you missed the first game, it's got a visually improved release that slightly uses the tablet (for item management, I guess).
Wonderful 101: Another well-reviewed game I didn't play, but it seemed like something that should be mentioned.
Xenoblade Chronicles X: It's not out yet, and I haven't played the first, but it's supposed to have online co-op. I'd give it a try, if I had folks to play it with online.
Hyrule Warriors: Decent scores, but I'm not a Zelda person. If you are, and you're into hack-and-slash stuff, you should be pleased.
Kirby and the Rainbow Curse: Respectable platformer. If you like Kirby, you'll enjoy it. It, unlike YWW and DKC:TF, supports 4-player co-op, if I remember correctly.