Did you even try to research this yourself? There are many mutual funds that have 20%+ YTD. It's typically recommended to invest before paying off debt like student loans/mortgages because you're likely to make more investing than what you'd save on interest.
You're talking about historical returns of 20% which have little bearing on future returns. (This is finance 101 stuff, let me know if you need a link that explains it to you)
Paying off a 5% interest debt gives a guaranteed return.
Sounds like you're the perfect candidate for the next Bernie Madoff... he guaranteed future returns of >10% on his mutual funds :-)
That said, a (heavily conditioned) case can be made for investing before paying off loans, as I did in my original comment for this thread.)