i haven't played HALO (just tried it at a friend) it didn't appeal to me..... from action genres i would go for jedi knigts and mafia.... even Max Pane which is a classic shoot em up game has a story.
I just mentioned that to some people (i like to think a lot of ppl) the story is a selling point. OK if it was a combat simulation that could be used for training the commandos of the future there's no need for story hehehehe i would play it anyway