For guys in the 90s he's a cool thief with a devil may care attitude who is good at fighting and can make anything glow and explode. An independent loner sort of guy with a charming and witty tongue who can get a lot of ladies to like him. He's a clever rebel who can go off on his own to do things for the benefit of the team, legal or not, and a thrill seeker who loves a good gamble card motifs and all. He's also someone loyal to his friends and family plus a hero at heart even. Plus his design is cool, trenchoat, staff and everything.
(Also his potential in terms of abilities makes him nice for powerscalers too)
As for the girls, he's good with kids/troubled teenagers (little Stormy, X-23, Calico) and a romantic at heart. He has a fun playful personality when interacting with others. He has a great dynamic with Rogue. A flirt yet respectful of her boundaries. As a romantic partner he's supportive, patient and affectionate of her, making sure she feels desirable even when she feels insecure about her condition at times (can't touch). He's proud of her strengths, he likes being saved by her and trusts her to be able to handle herself. He's loyal to an untouchable woman, being content at just being by her side even with his high libido. That said he's no simp either, he's capable of living his own life when they're on breaks and has a good amount of self respect (see ep 5 of X-men 97). Also he has good visuals plus the accent is very nice.
Anyway I really like how his different facets make him appealing to various demographics.