Lately my friends and I have been using this team comp.
Top > Riven or Malphite
Jung > Amumu
Mid > Kat or Akali
Bot > MF / Kayle

We start by amumu ulting, then kat ult's, then Kayle gives kat the ult and then Mf ults and Riven give consistent damage. Would like to know if this is a good team comp, and/or some recommendations for better ones.

Indeed, this team comp is a mighty force.

The trick to good team comps is synergy. The comp you outline is a powerful teamfighting setup, so you'd want to use it to force fights on objectives to win. The big glaring weakness it has though, is a lack of poke or waveclear. That doesn't mean your comp is bad, it just means that you need to be aware of such a thing. You could mitigate it by changing champs around, but you might be sacrificing AoE ult power to do it.

There's a lot of different strategies that work in the game. Your comp is best suited to stomp around as 5 and force fights whenever your ults are up. Other comps might be best suited to trying to stall while whittling the enemy team down with poke (your comp is well suited to counter this strategy though, since you can pretty much tower dive at will). Others might be built around a tough defensive team with a split pusher (your team would be weak to this since they'll have someone like Janna or Alistar to reset the fight, and losing anyone from your group weakens your wombo combo significantly).

There are more than those too, but I hope you get the idea.

In all comps there are strengths and weakness. Overall, this comp is great in teamfights! Katrina and Kayle combo is really good.

the comp is good and annoying but good luck not having your key hero banned considering that malp and emo mummy is banned almost every game.

Thank all of you. My friends aren't lvl 30 yet so we just play normals. Cenerae thanks a bunch and we will update this comp eventually.