Back in the 90s and early 2000s, I sometimes become sad that a great enjoyment has come to an end.

Nowadays, i keep the game and go through the map if the game is open world like FC3 and GTAV. In that way, i don't get sad.

It depends. Most of the time I just move on, but sometimes I also get sad during the credits, especially if the game was very long with a great story. Many JRPGs make me feel like that.

I feel as though that game becomes a part of my identity, part of my life story somehow; it’s difficult to explain, but when I get really taken in by a game and its world, it almost feels as though I was “actually” in that world. It’s as though I’ve “lived” that life, that experience, and I’m left walking away from it changed somehow. I think the games that always spring to mind that have had these profound impacts on me are Ocarina of Time, Majora’s Mask and The Witcher 3. I have not explained myself well at all with this post, but it’s genuinely because I find it difficult to accurately convey what it is that I feel/experience/mean. When it’s over, it’s almost as thought it’s never truly over as it lives on inside me. I hate that I can’t describe coherently what I mean! I love that gaming can take me away in ways nothing else can.

Some times I don't even finish them, because I decide I have to do certain things before that. Which I don't end up doing.

But when I do finish games I like, it can be a positive, negative, or bitter sweet feeling, depending on the game.
Some times I'll miss that world and the characters, knowing that I probably won't see them again. Other times I feel like I've had my fill of this world, and it felt like a good time to say goodbye.

I recently re-visited a world and characters I really liked from .hack/G.U. in the new vol. 4 sequel, over 10 years after I played the original. And it was an interesting experience because I felt very different about a lot of things than I did before, and it made me wonder if that was because this volume received a lot less development time, if the town always looked this empty but I just never noticed when there was no HD, or if it's because it's actually made to be more empty due to story reasons, etc.

Been thinking of making a thread about it at some point if I can formulate my thoughts better.

A good game? Probably content and ready to move on.

A great game? A little sad it's over but excited to see where it falls on the rankings.

Project X Zone? I want to go back in time and prevent the gaming industry from ever happening. May be a slight overreaction, but that's how much I hated playing and beating that game.

I feel clean. The sun is shining, the flowers are blooming, the crops are growing, the ocean is calm; peace has been achieved.

If it's a particularly great game that genuinely resonates with me on a deeper level it can leave me feeling empty for a while because the experience I was enjoying has come to an end. That usually means that I don't want to start any other game for a little while.

I usually makes me a bit worried that I won't be able to get into another game like that for quite a while after. Which is often true. And I end up playing games much less for a while. First I'll draw it out as long as I can though. Take screenshots, sometimes create timelapse videos, do everything but following the main story. However at some point you run out of things to do and the game comes to an end.

If it's a tough or meh game, I usually feel relief if I finish it.
With a lot of games, it's a bittersweetness mixed with satisfaction.

I've been playing Civilization for 25 years and I'll never finish that, version numbers might change mechanics have evolved but I'll never be finished with Civilization. Sure sometimes I take a brake and don't play Civ for 2 years. But I always come back.

Aside from Civ, I usually feel pretty content and just quit, there are quiet a few games that I have to force myself to finish because I feel content before the actual end.

Only game (in the past 20 years at least) that have left me kind of empty was BotW. The feeling I miss is the exploration when the world was new to me. And that game was as above, I mucked around a lot and explored and then I beat Ganon and then mucked around a bit more but just finally felt "done" with the game. I've tried to pick it up again, but the awe of exploring a brave new world simply isn't there any more for me, so I leave it up to the memories of exploring the game initially and a bit sad feeling that it will probably be another 20 years before another game like that appears.