I took four years (?) of Spanish in high school, but I've lost most of it by now. Like kadelette, I'd say that's probably because I rarely used the language outside of class and didn't have a particularly strong interest in Spanish or Latin American culture at the time.
In college, I took a few intensive language courses in German and really got into the language. Being interested in the language, practicing it for fun with friends, and studying abroad in Germany led to me learning far more German in about two years than the amount of Spanish I learned in four years. I'm still a long way from being fully fluent, but I've learned a lot. I'd say I have a working proficiency, but I can definitely get by in an ordinary non-technical conversation and I've been told that my writing is strong for having just picked it up in college (Germans love sentences with tons of clauses and so do I