I'm not a straight guy, but I've always loved shoujo manga. Sometimes I don't want to read about adult ideas and adult relationships; I'd still like the fantasy of a magical romance and a prince who is almost too perfect, to sweep me off my feet and take me away to his wonderful land of romance and perfect love.
My favorite is the 70s for shoujo manga: so many sparkly eyes, long legs, and painfully beautiful men. One of my very favorites is Eve no Musukotachi by Aoike Yasuko. I tend more towards comedy and silly stuff, although I do admire the ability to write a dark, gripping story like, say, Kaze to Ki no Uta, which is just too much for me.
Do you know Patalliro!? That is one of my favorites of all time! It's still running, too. Mineo Maya is incredible.
Part of what I have always loved about specifically shoujo manga is the optimism and pervasive cheer. There's a kind of magic in a lot of those stories. But there are so many stories for girls that are very deep, or even dark, or serious, or depressing. It's not just sparkles and romance, though that's my favorite part of what tends to come to mind with "shoujo manga". Many stories written for girls have a profound emotional resonance that is difficult to convey; the aforementioned Kaze to Ki no Uta is so heart-wrenching that I can't read it, but I deeply admire the artistry that created it.
Something else, which many don't know, is that several important and well-known shoujo mangaka are men. Mineo Maya, for example! Of course, the sociocultural landscape of Japan is so confusing to many who weren't born into it...
Anyway, there are many men who read shoujo manga, and plenty who create it too!