Here's my view on this:
If a game is really great, I'll pay money for it. In conclusion this means that If I can't actually try the game, I am not going to download/buy it.
A game that's worth my money has to have:
-nice visuals
-good gameplay
so making another endless runner or angry birds like game will most likely disqualify you from being purchased, be unique.
noteable games I purchased in the past:
Xbox Live
- Tentacles
- Asphalt 7 (superior to 8 because it does not require IAP to be enjoyable)
- FC Rocket
- Geo Defense & Geo Defense Swarm
- Project Sunburst (Sadly defunct)
Indie Games:
- Infinite Flight
- Pixel Shaper
- Steam Birds
Also, if it's a casual game I am willing to pay less, "proper" games are worth more to me (allthough not $13 for a remake like Final Fantasy III)
Having said that, I am also ok with ad supported games, especially if they're casual games. The only thing I ask is for the ads to be non intrusive. They shouldn't hinder gameplay in any way (by using screen estate or pausing gameplay), they can be in loading screens and menus.