For me, Hysteria will always be on top. There just isn't a song I don't like on there. I also think it sounds the best of all their albums.
I used to hate Adrenalize, but I gave it a second chance and one by one it grew on me. There are still two songs on there I don't listen to, but I like the rest. I found that it seemed to follow the natural progression of their sound from HnD -> Pyro -> Hysteria -> Adrenalize. Adrenalize is where it becomes too a bit too poppy for me though, which is why I rank it lower.
Euphoria is a good album with a couple bad songs on it IMO. A lot of the songs sound like classic Def Leppard, and then there is some 90s pop songs stuck right in between. It also suffers from a bad mix I think. I would love to remix that album. All of the sounds are there, but they aren't in balance with each other like they should be. Perhaps that may just be a product of the times.
For their recent output, I don't know. I just don't like how it sounds. Some songs on Sparkle are ok, but to me they sound like standard rock songs (and instrument sounds) with some Leppard elements thrown in. That's why I'm not excited at all about them starting to record a new album. When I think of Def Leppard I just can't get past that huge 80s sound. Somehow I doubt that any new release will have that.