I have a set scoring system that I devised to try and take time and nostalgia into account. I score the following out of 10 then take an average:
Score I gave or would have given the game when I first played it
Score I give it based on modern standards
This really is a personalisation score. Some games I simply remember fondly even though I know they're objectively not better than others, some games I just really like the setting or certain characters.
Amount of time played:
The amount of time I personally devoted to playing the game.
I find this helps balance my list as I go down and change the modern and emotional scores every year. I actually have around 200 games ranked in this way from doing this exercise in previous years, lol.
I like the "emotional connection/nostalgia" aspect of this. I can't possibly gauge things like that in a tangible score because I find it's subjective enough to change sometimes from day to day for me. It is the only metric I use though. I mean what else matters, frankly, other than what a game means to you? Anyone who uses a different metric to determine their favorite games is a fraud who just wants to be popularz, IMO. My list will be completely non-objective, to that end. A favorites list to me is exactly that. It's not a list of the 50 objectively best-designed games evar, it's a list of games that have meant the most to me and/or brought me the most joy.
Every scoring system will have some bias to it, but I wanted to have a way to score that encapsulates when a game that I know has been polished and displays close to perfection (and is therefore enjoyable) vs a game that I know is technically less polished, has more annoyances/bugs but has a setting, environment, art style etc. that speaks more to my personal preferences.
As an example: Assassins Creed: Odyssey vs Red Dead Redemption 2
I played both for the same amount of time, but Red Dead Redemption 2 in nearly every way is a more complete package, right down to the horse riding system and animations through to environmental details, writing and characters. I enjoyed playing through and appreciated the depth and detail, but the setting is completely forgettable to me. Therefore, Odyssey ends up with a lower Initial and Modern Score, but higher average as the I love the ancient Greek setting and the emotional connection is much stronger.
By the same boat, the Initial and Modern scores are tailored to account for the difference in older games. Nearly all PS1/N64 games for instance have aged badly, but were revolutionary for their time.