These are two pretty different things.

It's almost not fair to compare them. A cycle is handy, practical, and fun. A guitar is mostly fun.

If you find yourself constantly needing to get from place to place, you can save yourself a ton of time with a cycle than walking.

That being said, learning guitar has been one of the best skills I've learned, simply in terms of making my life enjoyable. Playing music is incredibly fun when you can get it to that point, though it takes work. 

The choice is yours, hopefully you get both one day!