first of all i want to clarify that i am talking about at the time (im pretty sure you already knew that). right now, gamecube games have skyrocketed so it is even more expensive to game on that than the current wii u. right now, it is the best time to get wii games because im sure it will be like the gamecube in that the games will skyrocket in five years time. i also believe once the wii u has been dead for five years, you will see many games be 60 to 70 dollars a piece. 

that being said, at the time, you could have always got the excitebots and excite truck games for cheap, and nintendo came out with the nintendo selects (in 2010 i believe) where their most popular games were discounted to 20 dollars. the big thing about the wii though is that it had a lot of great third party games for cheap. de blob, boom blox, muramasa, mad world, no more heroes 1 and 2, red steel 2, i could go on and on. there was a lot more to buy a wii for than just nintendo games. so if the OP were making this thread about the wii in 2009 or 2010, it is way different than making this thread about the wii u in 2015. its just different. (sadly :/) with gamecube, all the nintendo games retained their value, but they did have players choice relatively early in the life cycle if im not mistaken where they discounted the games. 

I'm sorry, but you can Ninja Gaiden 3: Razor's Edge for less than 10 NEW for Wii U, with free online play, off-screen play, and different controller options... Again, for LESS THAN $10. 

Need For Speed can be bought for $20 at Wal-Mart, it includes improvements over the 360 edition, free DLC content, new content and modes exclusives to Wii U, and it is a well made port.

He already has Batman, and the other games he didn't mention.

Anyway... You can also get the definitive console version of Sonic & All Stars Racing Transformed for $20 or even less on eBay (New, of course). It has exclusive modes for Wii U, plus support for five people in local and online multiplayer (you can play with up to 12 people, and 5 of those can be in the same room as you, amazing!).

Sonic Lost World can be found for cheap nowadays as well. I haven't played it, but the demo was nice, and it has gotten updates since the release... Which covered most of the issues that it had (such as not gaining a life after getting 100 coins). The Deady Six Edition with bonus content can be found for cheap online, and if you're lucky... At stores for $20-30.

As the Demi-Fiend wrote, Monster Hunter can be found NEW for cheap, and it is a massive game with hundreds of gameplay hours.

And if you're looking for used games, then eBay is your best choice. You can get both, new and used games from small/medium sized videogame store chains for very nice prices.

i do agree that free online on the wii u is great, and makes certain multiplats like call of duty better to get on the wii u. im in full agreement with you there. 

but look, if youre buying the console for sonic racing, need for speed, batman and ninja gaiden 3.. i mean.. its just not the right console to get. the 360 has all those games times 200, and theyre all cheaper. to get the most out of your wii u, youre going to be stuck paying for expensive games. plus, all these games youre talking about are like three years old. there is handful of games, some slightly better, and some slightly worse than their multiplat counterparts but the thing is, there isnt going to be any more of those to get. those are all 2012/2013 games and there are no more on the horizon.

i don't think the OP wanted newer games a lot since it was mentioned that he would love to find out discounted games, i doubt any newer games would be discounted on the price he wanted.

I'm not sure if they will all of these are $20, but none of them should be over $30.

Injustice - A DC Comics fighting games from the makers of Mortal Kombat 2011 and MKX. The online community is probably dead by now, but I enjoyed this one more than some other fighters. As made obvious by the Teen rating, this is not Mortal Kombat: DC Edition. The game has a diverse group of 24 fighters, both heroes and villains. One fun aspect is that each character has a button tied to their unique abilities. FWonder Woman can switch between her Whip and Sword for different moves, Lex Luthor creates a force field, Green Arrow gets a number of weaker ranged attacks, etc.

Monster Hunter 3 Ultimate - The original Wii game was huge and amazing, but the Wii U version is the definitive one. You get you Monster Hunter Tri, throw in HD, better online multiplayer, cross-compatibility with the 3DS version, and the GamePad for menus and HUD in addition to basic new content. This is a series of big meaty Action RPG's, and this is probably the best in the series on consoles thus far.

Nintendo Land - A former bundled game, this is quite cheap to get used nowadays, maybe $10. Think of it kind of like Wii Play in how it shows off the GamePad, only with more substance. Out of the 12 minigames, some are better than others, but the three "Team Attractions," which can be played alone or with others, are worth the $10 by themselves. The Zelda-themed action game lets you use either the GamePad as a bow or the Wiimote as a sword to beat waves of baddies. "Pikmin Adventure" is sort of a simplified combat-oriented imagining of the series where friends can play as Pikmin. Metroid Blast is my favorite: a third-person shooter where the GamePad can be used to pilot Samus's ship. All three have proper campaigns to play through. The remaining nine minigames are less substantial, but this is well worth $10.

Resident Evil: Revelations - Originally a 3DS game, Revelations was ported to consoles because it was the best Resident Evil title Capcom had made in a while. The game tries to compromise between the past roots of the series and the new action elements. It doesn't always succeed, but does far better than RE5 or RE6. Note that in addition to the main story, there is an action-oriented Raid Mode that complements the action orientation of the series. Just remember that even with the HD makeover, this game started on a handheld, and thus won't graphically dazzle you.

Warriors Orochi 3 Hyper - Big action game where you slaughter thousnads of enemies as one of over 100 playable characters. As a launch title, it suffers from performance issues, but might be worth a look.

Wonderful 101 - Platinum Games, in between releasing Metal Gear Rising and Bayonetta 2, released this quirky action game back in summer 2013. It lives up to their reputation. You play as a team of cheesy superheroes fighting off an alien invasion. Things become increasingly epic and silly from there. Has some incredible boss fights.

ZombiU - You mentioned you were getting this, but I felt it warranted another mention.

Well, might as well tell the TC that he/she made a mistake for buying a Wii U (Which I assume TC has done so already, or will today/tomorrow). TC is asking for recommendations on games that are cheap and worth playing, not asking for the newest Forza, Super Hero, etc. Is it hard to just recommend the games that are already out for a new Wii U owner, instead of saying that the 360 has better and cheaper games? 

Anyway, I would also recommend Tekken Tag Team Tournament 2... Target might have it in stores for $20, used copies are more expensive than that.

there are plenty of games id recommend, theyre just all expensive

ZombiU and Wonderful 101 are both $20 new, so used should be a little cheaper.

Nintendo games, especially the big hitters like Splatoon, Super Mario Maker, Smash 4, 3D World, MK8 etc. will almost never get a price drop to $20 brand new so it's really hard to find good deals for these games :/

^ Target had MK 8, Smash, and MP 10 at 20% off this past week.

You can get 20% off new games at Best Buy if you have their 2 year $30 membership.