A genre that has 2 teams, small environment and no levels looks like an RTS for me.
- Creates barracks that automatic spawn creatures to the other base ( the stronger the creature, the more time it takes to spawn ). - The creatures follow the shortest path. - Put some environment in your map so you, as player, need to build your barracks on a good spot so your creatures will reach the other side faster. - Get some economics in it so you need to balance out your base with barracks <-> income. Smart building means more chance to win!
The fact you are asking what language best fits means you know basics of different languages or just don't know a single programming language. What language you should take depends on yourself. I like programming in C++ because it has no limits. Java is written in C++, don't uses a stack, so only heap for every object. I don't know anything about other languages.
Or a competitive puzzle game - Come up with a simple, fun-to-play rule system and look at different ways for the AI to evaluate their moves. That way you can focus on developing a challenging (but not all-knowingly impossible,) group of opponents that specialize in different strategies. Tweaking them for personality as opposed to ruthlessness will help you design believable AI that are satisfying for users to play against, an important goal for a game AI designer.