Haven't got the time to check out many games but I think I know what you mean. Well, I hope my game feels complete enough, haha. On the other hand, everyone needs to evaluate their own goals. Throughout development of my game, I was asking myself is this the whole thing? Is this feature complete? And I would love to add more stuff and continue working on polishing little details etc. but there is a point where you have to say stop, I'm satisfied, ship it, and move on. As for me, I'm pretty happy that I managed to really go back to my project and wrap it up within a month. Having it very half-baked on my hard drive was driving me nuts.
All in all game jams can teach you a lot of stuff about how to manage your time, priorities, how development under pressure feels like. I hope as much people learned some good lessons on this. Doing games is fun, but finishing them is a real struggle.