It seems there are basically two types of triangles in shoujo:

1. mysterious powerful guy vs childhood friend or next door nice guy.
   The second one always wins. The first one turns out to be mean and evil or meets a tragic dramatic end.
   Why? Isn't shoujo supposed to be this unrealistic romantic fantasy?

2. mean & bad-tempered guy vs sweet & well-mannered guy.
   The first one always wins. The second one turns out to be an evil liar or becomes a brother figure.
   Why? Does well-mannered equal boring in the eyes of the general audience?

Lol, from what I've seen though, majority (emphasize on majority) of the time it's the guy with black hair that gets the girl.

Quote from ForteAtrox

Lol, from what I've seen though, majority (emphasize on majority) of the time it's the guy with black hair that gets the girl.

This. XD

Hmm, lemme recall a random love triangle...16 Life, winner was the mean black-haired guy, losers were the nicer (and non-black-haired) guys. But manga like those tend to have a main focus of being popular with the readers. Less shallow ones like Sora Log make the characters less two-dimensional.

...That said, it took me a long time to think up a non-shallow shoujo manga. A lot of shoujo tends to focus on following trends. I guess maybe a lot of the less shallow ones fall closer to the josei genre...?

Beauty is the Beast is non-shallow I think.