I'll be honest, I'm cynical and critical at the same time. Being both doesn't make me any less of a fun person to be around. I'm very judgmental, but I know to keep my opinions to myself, especially when it comes to the negative things I have too say.
I think being cynical or critical is fine as long as you aren't incredibly stubborn to push your opinions onto others. That's what can make you an unlikable person.
It's hard to say if it's "good" or not either. Considering it can dampen your mood sometimes assuming the worst in everything, but it can also keep you strong in cases that do actually go wrong. So it's sort of 50/50 I think.