Let's see a ranking of your lenses, from favorite/most impressive vs. least favorite/least impressive. Here's mine (lenses I currently own shown in bold):
1. Canon 35L 1.4 - Picked this up for a great deal on Craigslist, essentially brand new. I intended to turn around and resell for a profit, but man, I just love everything about this lens. I don't know if I can afford it but I hate to give it up.
2. Canon 70-200mm 2.8 IS - Just a solid performer, fast AF, sharp, beautiful bokeh, great contrast & colors. Really I have no negatives to mention.
3. Canon 100mm 2.8 macro - What an awesome, sharp lens. Along with 35L probably the sharpest lens I ever had. Had a lot of fun with it but sold it since I didn't use it enough to justify keeping, but now I kinda wish I still had it. I picked up some extension tubes but they're just not the same.
4. Canon 100-400L - Great lens, I had a really good copy and dumbly sold it because it was a lens I didn't really "need". (I do mostly weddings) Probably the lens I most regret selling.
5. Canon 24-70mm 2.8 - Same characteristics as mentioned for the 70-200, another solid lens. Kinda boring, but gets the job done every time.
6. & 7. Canon 10-22mm and Canon 17-40L. Had the 10-22 on crop and now the 17-40 on full frame. They're nearly identical lenses and both do their UWA job very well, no complaints.
8. Canon 70-300mm IS - Was a really good lens, I chose it over the 70-200L non-IS and didn't regret it one bit. Had to sell to fund 70-200 2.8IS though.
8. Sigma 30mm 1.4 - This was a pretty darn good lens, if it worked on full frame I'd probably have it rather than the 35L. The 35L beats the 30mm 1.4 in every aspect, but not by much. For the price the Sigma version is a great value.
9. Canon 17-55 2.8 IS - A love/hate relationship for me, mine was really sharp at 2.8, maybe even sharper than the 24-70. I had to rank this lens a little lower though because my IS failed after 2 years, and the inner lens elements got quite dusty. A really fast focuser overall, but I also had some front-focus issues on 40D.
10. Canon 18-55 kit lens - For what it was, this was actually a decent lens and gave me some good shots, no complaints.
11. & 12. Canon 50mm 1.8 & Canon 50mm 1.4. For some reason I haven't been able to fall in love with either of these 50mm lenses yet (haven't tried the 1.2 version). I'd call these two lenses decent but not spectacular. I would like a little more sharpness & contrast wide open out of the 1.4, and better focus & bokeh from the 1.8. I'll likely end up selling the 1.4 if I keep 35L.
13. Sigma 10-20mm. Hands down the most frustrating lens I ever owned. I tried 3 copies and each had their issues, mostly with softness on one side. I know lots of people have good luck with this lens, but the Sigma Gods were against me I guess. Ended up trading for the Canon 10-22mm and never looked back.
Well making that list turned out to be harder than I thought. If you asked me again in a few days the rankings would probably be in a totally different order.
What does your list look like? Don't be shy, give a ranking no matter if you've had 2 lenses or 20.