for my letterboxd, I think of it as 1-10 rather than stars (so 3.5 stars is 7/10), and I kinda rate like:

• 1-5/10: varying degrees of bad, did not enjoy… rarely use these ratings as I don’t tend to see ‘bad’ films
• 6/10: probably a fairly mediocre movie but I found it entertaining, worth a watch if it’s your thing (something like Crank/Crank 2 for example)
• 7/10: solid movie, nothing groundbreaking but also no obvious flaws, entertaining enough
• 8/10: the sort of movie you’d start to recommend regardless of someone’s general preferences, no real flaws but also probably not particularly innovative, just a standout film of its genre
• 9/10: the sort of film you could see someone including on a ‘best of all time’ list, an easy recommend for most people, does something above and beyond what you’d expect of a film in its category… you’ll be thinking about it the next day
• 10/10: highly personal and perhaps not even a film I’d generally recommend, but for me this is a film that leaves a deep impression, I think if I gave someone a list of my 9/10s it’d be a fairly generic list of good movies, whereas my 10/10s would be pretty eclectic (perhaps with some questionable choices) but they’d reflect me as a person… I also tend to go a bit more in depth when I review these ones

there’s also the ‘like’ option, I use that when I want to rewatch a film… so it’s possible I might see a film I rate as 9/10 but don’t ‘like’ it - that just means I recognise it’s impact and artistry but it didn’t necessarily resonate with me