I think you need to be very careful not to romanticise one attractive quality in someone else and compare it with the whole reality of the partner you actually have.
You’ve described a man who is emotionally intelligent, mature, kind, thoughtful, consistent, great with your children, sexually compatible with you, treats you well and who you can still laugh and tease with. That is an incredibly strong relationship foundation, and frankly, a lot of people would give their right arm to find that combination.
Your colleague being naturally hilarious is lovely, but you’re seeing him in a very specific environment where his best quality is on display. You have absolutely no idea what he would be like as a partner at 7am when somebody is ill, when money is tight, when the kids are difficult, when you’ve had an argument, or when life becomes boring and stressful. Being funny does not tell you whether somebody is kind, dependable, emotionally safe or capable of maintaining a healthy relationship.
And it’s worth remembering that your partner probably doesn't think you embody every single quality he could possibly find attractive in another woman either. There may well be women who are funnier than you, calmer than you, more spontaneous than you, more interested in one of his hobbies, or possess some other quality he occasionally wishes you had. That doesn't mean he'd be better off with them.
No partner is going to contain every desirable characteristic that exists in every other person you meet.
So yes, I think YABU if you're genuinely feeling sad that you're “missing out.” You aren't missing out on a better relationship; you've simply encountered someone who possesses one quality your partner doesn't possess to the same degree.
I'd appreciate what you've got rather than allowing an imaginary version of somebody else to compete with a very good man who is actually showing up for you in real life.