I'm not sure of this myself - I plan on only developing for the PC market anyway - but you should access the Android and Apple app stores and check out some of the genres and reviews. Also check how many reviews are from paying consumers, and these combined should give you a rough idea. You should note, though, that just because a game similar to yours might make lots of money, that yours might not necessarily make as much, or gain as much attention. This is where self marketing comes into play, and is well worth researching.
Additionally, I think it's a good idea personally to keep an equal balance on your passion for development versus passion for earning money, as the latter can heavily influence the former and not equate to good decisions (I'm looking at you, EA).
At any rate, I wish you luck with continued development, .