Considering only games that people would (generally speaking) call "Good" games development budgets on previous generation consoles ranged from (about) $2 Million for low budget games (like Starwars: Rogue Squadren 2) to roughly $20 Million for the biggest budget games. In this generation the Wii's games stay in a similar budget range to previous generation consoles (with a far greater number of low and ultra low budget games), and the HD console's games have hit a point where a low budget game is approaching $10 Million and a big budget game can surpass $100 Million.
Now, on average producing similar games for the Wii will cost around 1/4 to 1/3 as much as a HD game would. A few publishers have used this lower development cost to produce a lot of games in multiple genres, targeting multiple demographics, at various budget levels in order to have very reliable revenues from the Wii ... While few people really love Ubisoft at the moment you can see how they follow this approach, and they (probably) were able to develop Shawn White Snowboarding, Rayman Raving Rabbids: TV Party and several licenced games as well as buying rights to No More Heroes for the same ammount as it would cost to produce a fairly average HD game. When you look at a game like Assassin's Creed you might think that (from a business perspective) their strategy for HD consoles is better, but for every super successful HD game there is on or two (potentially more depending on the publisher) that struggles like Haze did ...
