I actually started my collection with a UCS. From then, it's hard not to look for big sets (Modulars as an example) to buy hahaha. Then I started getting myself poisoned for other themes. For superheroes, I actually got all sets released last year except for Wolverine and Batwing over Gotham. Still thinking over them whether I should get or not. Then here are some themes that I have as well:
1. Lone Ranger - completed all 6 sets except for polybags.
2. CMF - some completed series and some random minifigs from older series.
3. Modulars - completed starting from Fire Brigade. Anything prior to that is too expensive.
4. Creator houses - Missing Apple Tree House and Lighthouse.
5. Advance Built sets - Only Tower Bridge but planning to get Opera House
6. SW - Some iconic sets that I wanted. Not really into collecting all SW. Just too many lol
7. City sets - Got most of the 2012 sets as well. Waiting for good deal on this year's summer sets hahaha
8. Black Pearl and Queen Anne's Revenge

9. Technic - Poison seeping in very slowly. Only owned 42000 but all the way at the bottom of wishlist has 9398 lol
wah reading from the list.. no wonder ultraman says you are the taikun!!!