Best Resolution for Cross-Platform

I'd like to develop a game that'll be available on all platforms (mobile, ipad, pc, etc...).

What resolution would be best for that? Should I have different graphics for each screen size? (e.g. different graphics for mobile and pc)

You are thinking too big. Start small. Get the game finished and working on an iPhone. Then worry about getting it out on other platforms.

Think about Aspect Ratio instead of resolution, to allow scalability.

Tekniko - It seems like something I must think about beforehand, otherwise it'll probably be a headache to adjust the whole game to a different resolution later.

I'm in a slightly more complex position than simply getting the game out on one device first, I must make sure that cross-platform is possible.

notnsane - Could you please elaborate on that with examples?

https://www.scirra.com/tutorials/73/sup ... reen-sizes

Most mobile devices are 16:9 or 16:10 aspect ratios.

720p is a safe bet, as it scales up very well to 1080p which is the most common PC/Desktop resolution.

I think this is the million euro question.

What resolution will run on all platforms ?

No such thing, since Apple uses 4:3 ratios on their Tablets and 16:9 on their Phones. So that platform you have to make two separate versions if you want your game to look properly.