I think mortal kombat and injustice series can be played 1 vs 1. In case of 3 vs 3, I'd recommend going with the battle royale games like PUBG and Fortnite. And in near future even the call of the duty.
Clash Royale is a pretty good 1v1 game on Android and iOS. And it's not too hard to get into right now and you won't have to worry about any pay to win aspects in this game.