I am asked to list "the best things in our company". I want to say that the team I am in is great. But I think it should be a noun to be filled in the blank to answer the question. So I think "being in a great team" should be filled in, am I correct?
Yes 'being' is a gerund and hence a noun. I suppose you could also use the infinitive 'To be in a good team'. But 'be' on its own does not, it seems to me, grammatically answer the question.
However I'm not clear that it answers a question about "the best things in our company". It seems like an answer to "Why do you like working in our company?".