As a 32-year-old fan of LEGO, I finally moved the boxes of LEGO from my folks' attic to the guest bedroom. Needless to say, the wife is not too pleased! My parents started me with LEGO when I was 18 months old and I still have almost all the sets/pieces from way back then. My mother used to laminate the instructions for me so I wouldn't tear/lose them. As a child I especially enjoyed the Castle and Pirate sets (boy was I bummed when LEGO stopped making the actual shooting cannons). As a teenager I loved the larger Technic & Model Team sets, many of which remained built until well after college.
Some of my favorite sets include 6383 Public Works Center, 6393 Big Rig Truck Stop, 6394 Metro Park & Service Tower, 6395 Victory Lap Raceway, 6671 Utility Repair Lift, 6399 Airport Shuttle, 8856 Whirlwind Rescue, 8868 Air Tech Claw Rig, & 8480 Space Shuttle. The Nautica series as a whole is also very good.
The Farm and Construction City sets recently renewed my interest and I'm in the process of buying those sets to build. I'm looking forward to the new Harbor and Pirates of the Caribbean sets due later this year.
My sets: http://www.brickset.com/search/?ownedBy=DaveBey
Cheers from Claremore, OK!