Lemme give you the lowdown. I've played more eShop games than retail releases on both the 3DS and Wii U- I know that's not a bold claim, but I have lots of OPINIONS.
"Must-have" eShop Titles:
-Fast Racing NEO- A steeper-priced eShop title, and maybe obsolete with RMX Switch on the horizon, but damn, this is a fast-paced, white-knuckle racer. Lacking in aesthetic charm and character a bit, it makes up for it with pure, unadulterated gameplay.
-Elliot Quest- This is the best Adventure-of-Link-alike title around, but it takes it to the next level with brutally difficult end game boss fights. Very open-ended, it's exploratory bliss at its finest.
-The Swapper- One of the most interesting blends of gameplay and story I've ever experienced, this puzzle-platformer is clever. You can get it elsewhere, and if you do have it already, that's okay. But if you don't, buy this game NOW.
-Scram Kitty and his Buddy on Rails- This blend of platforming and rail-shooting is one of the more novel and interesting experiences on Wii U, and it's odd spectator mode thanks to off-TV play is pretty silly. Atop that, it features a crushing difficulty curve that blends the best aspects of its individual genres in order to give a frustrating, but also extremely rewarding sense of accomplishment.
-Xeodrifter- Not Wii U exclusive, and loses the touchscreen functions present on the 3DS.
-Shantae and the Pirate's Curse- A fantastic Adventure-of-Link-alike, but marred by a pretty terrible stealth segment in the middle.
-SteamWorld Games- If you can't play these on other consoles, get them here. Duh.
"If you're into that sort of thing" Titles:
-Shantae: Half Genie Hero- It's not the best Shantae game on the Wii U, let's put it that way. An action-platformer with great art, mediocre bosses, and a mediocre soundtrack.
-Pushmo World- If you have played Pushmo on 3DS, you might not feel that rewarded by the slow difficulty curve on display here. If you HAVEN'T played Pushmo on 3DS, play this game!
-Q.U.B.E. Director's Cut- Do you like ball-physics, first-person puzzle games? THEN BOY DO I HAVE THE GAME FOR YOU!
-Child of Light- While the combat and customization options at play in Child of Light are fantastic and the art style is lovely, the dialogue and plot is pretty terrible, even for an RPG.
-Guacamelee- Do you want a melee-combat-based Metroid with a Luchadore theme and an uneven plot? THEN BOY DO I HAVE THE GAME FOR YOU!
-Freedom Planet- Do you want a Sonic game where you can run past enemies and get your ass kicked by the bosses? THEN BOY DO I HAVE THE GAME FOR YOU!
-Pokemon Rumble U- This genuinely fun series missteps a bit with arena-style challenges and is only redeemed by NEAR FIELD COMMUNICATION FIGURES (if you can get them).
-Shovel Knight- Do you like Mega Man games and whimsical dialogue, but hate yourself? THEN BOY DO I HAVE THE GAME FOR YOU!
"This game will try you but if you stick with it, you'll really enjoy yourself" Title:
-Chronicles of Teddy: Harmony of Exidus- This would be the BEST Adventure-of-Link-alike on the Wii U if it wasn't plagued by technical bugs. It will crash. Unless you save mercilessly, you will lose progress. If you manage to get past the first "world," it's smooth sailing and the rest of the game is absolutely fantastic.