Ooh, character customisation is pretty important to me when playing a human/humanoid character! There are always exceptions, though!
The ideal level of customisation varies per game. With some games, it's nice to have sliders to adjust every minute detail, whereas with other games, having some preset options to choose from is fine (e.g. preset faces).
If I had to rank the options from most to least preferred, it would probably be: good quality preset options to scroll through (e.g., face shape, eye shapes, hair styles, hair colours, etc.) > highly detailed customisation (e.g. sliders for adjusting things like eye size, etc.) > a single preset main character > a roster of preset main characters to choose from. Hopefully that makes sense!
I don't tend to want to play games where the player character doesn't appeal to me, so for that reason, customisation is helpful!