First fictional crush? Probably some boy in an Astrid Lindgren Novel - Borka Borkason in Ronja Robber's daughter, Kalle Blomquist (although I could never really choose between Anders and him; poor Eva-Lotta!), Madicken's Abbe. Astrid Lindgren could write rather crush-worthy boys... Sensitive, but courageous they were always up for anything fun, but could be quite mature when neccessary.
And of course a lot of cartoon crushes - I'll join the Disney foxy Robin Hood harem. I also kinda liked Mowgli. And Bernhard from Bernhard and Bianca. Was always rather bored by most of the proper princes though (except for Mulan's captain, but I guess he doesn't really count as proper prince). (I'm still not quite over crushing on cartoons... Spike Spiegel, Mugen, Jin from Samurai Champloo)
Literary crushes, maybe not entirely designed to be crushed upon:
1) Ulrich in Man without Qualities. The very definition of every conceivable kind of privilege, he finds his life so lacking in any kind of challenge, that he sets himself an artifical one by deciding to kill himself if he doesn't succeed in giving his life some purpose in the span of a year. I was very impressed because I found him so intellectual. Yeah, I was in my late teens, early twenties then... (I still love the book. No longer crushing on Ulrich though).
2) Hans Castorp in The Magic Mountain. He also wants to be an intellectual, but he doesn't quite get there, before he's - Spoiler Alert - tragically probably killed in the First World War. Lots of tender feelings for poor Hans. His cousin Joachim is even more heartbreaking in his dutiful simplicity, but he's consequently quite a bit more one-note.
3) Robbie Turner in Atonement. Another tragic young man, felled in his prime. Persecuted innocence. And a bit like an Astrid Lindgren hero grown up, I imagine. Portrayed by James McAvoy in the movie, certainly a contributing factor.
4) Don Gately in Infinite Jest. A thief, murderer and ex-junkie, probably the closest thing to a bad boy on my list. But, yeah, tragic childhood and everything and also he's in rehab and he's struggling so heroically. Writing it down makes it sound so trite. It's not the "uh, sexy" kinda crush; he's just gving me all kinds of feelings.
I also had a bit of a soft spot for Holden Caufield and Angel St. Claire and Peter Walsh (the returning expat in Mrs. Dalloway), who are all ultimately rather disappointing - a certain weaknness for the self-righteous judgey types, I guess. But that's often the problem if you get too much of their perspective - it can nip the blossoming crush in the bud.