I mean “cool”, “nice”, “great” specifically in the generic sense of, if someone is talking to you and they say they did something nice and cool but not amazing or spectacular, you know, something ordinary but cool, like "I just went fishing this weekend", what is a generic way to say "oh, that's nice" or "oh, that's cool". Not cool in the sense of suave, sexy, popular or anything like that. Just a generic and polite way to reply to something someone said they did or something they saw or ate, etc., or that they are going to do. Like, "very nice" for instance.
It's not so easy to give a common answer, you can use one of the following:
Forte (a little childish)
but I usually skip directly to a follow up question, like
Ti è piaciuto?
To better continue the conversation.