Varies for me.
The last 2 years (mid to late 30's) have been great watching my daughter grow and my oldest step-son getting accepted and attending college. I would say the last 3 years have been the best years for the family and career. Prior to meeting my wife, I would say 25-30 was awesome when I was single; I was a IT consultant living the House of Lies stereotype for consultants (work hard and party harder when not working), but my girlfriends were front desk staff at hotels I lived in and when I was home at my place it was very lonely. Glad I stopped doing that and met my wife at 30.