Yeah, you're right. Girl's skinny jeans are usually skinny, meaning snug to the skin, but some aren't. Guy's skinny jeans seem to be anything that's just less baggy than whatever their baggy jeans are. Lots of them are no skinnier than slim straight legs, which are about 15 inches in diameter.
Skinny jeans should have a leg opening of about 12 inches, and cigarette legs should be about 10 inches.
Lots of girls, and we boys who like skinny jeans, think they should fit us like they do girls: form-fitting, or touching the skin from the waist all the way through the calf.... All the way to the ankle is good too, but those are harder to find, even for girls, but esp. for guys cuz our ankles have bigger bones than girl's ankles do, and we can have a harder time getting 10 inch openings on over our ankles, if at all....
They don't need to be TIGHT, but since they stretch, they should and do fit snug, but not uncomfortably so. Some girls recommend that you buy tighter ones than looser ones, cuz they will stretch out a little when you wear them and you don't want them to be baggy anywhere. A girl told me once to get them TIGHT, and wear them on Friday if I wanted them to look perfect on Saturday!
You shouldn't have to wear a belt with girl's jeans, cuz they actually fit and won't fall off without you holding them up with one hand. Guys jeans that fit won't need a belt either, usually, cuz their waist is a little higher and really fits over your hip bones.
Some girls don't like skinny jeans at all, on girls, or on boys, but they're probly pissed off at something else, like they can't wear them or something....
So, ignore the ones who don't like them, and ignore the ones who say that jeans made for girls should only be worn by girls.... They're just jeans, and NOBODY CARES if you wear "girl's jeans" or not. Most of the time you can't even tell....
Go to the store and check out the real skinny guy's jeans, and the skinny girl's jeans, and try them on. The staff are usually really helpful, and some of the girls get a big kick out of it if you're super cute! There's more girl's skinny jeans to choose from, more colors and washes, and they're softer, more comfy, and CHEAPER most of the time.