I was in the same boat once, having owned a guitar for a few years but only playing little pieces of simple songs, like Sweet Home Alabama and Stairway to Heaven. Problem was, I was a big jock-type and spent all my high school days on the practice fields. Now I wish I had been playing guitar!
Here's what you gotta do to get good on the guitar:
(1) Stop playing those little intros and start practicing ALL your chords until you get proficient with fretting them clean and changing them fast. You can make simple chord progressions sound different (like G-D-C) by lifting a finger here, hammering on a finger there, etc.
(2) Get some tabs from the millions of web sites out there. Learn to play your favorite songs--all the way through. What kind of music do you like?
(3) Experiment with sliding simple open chord positions up and down the neck, like C or D or E or F. Or make up your own using two or three fingers in a manageable position. You can get some cool sounds that way and you feel like you're being innovative.
Let us know how it goes, buddy. You are not alone . . .
DC
"It's all right son . . . we told you what to dream"