If you are serious and want your game to sell, you have to make a high quality game. Major portals will not accept any game that has poor gameplay or graphics. With a good game, gameplay and graphics go hand in hand. Developers must balance the two.
When designing your game keep this in mind. It’s much easier to make a cartoony looking game rather than something that’s realistic.
When you’re done with your game, go back and look at things that could be polished. There’s no reason why your game shouldn’t be the best that it can be. Spend at least a month tweaking as much as you can. Beta test your game and get feedback!
Mediocrity is not an option in this day and age. There are too many indie games being released every week for your game to get noticed if it looks or plays bad.
Why would you want to waste months to years of your life on a project and not have it sell well?