For me, it simply boils down to GOOD MUSIC! I'll listen to any genre that features, what I call, GOOD MUSIC.
And, IMO, the SINGLE most important factor is good music is EMOTION. Nothing more, nothing less.
I was into Opeth before Katatonia & PTree (never heard of Isis).
What attracted me (first) to Katatonia was the fact that Mikael did the vox on BMD. I purchased it & just loved the dark, almost "claustraphobic" vibe on that record. But, after their change in style I began to like Katatonia EVER MORE! I feel that their last two record are their best, easily topping BMD.
And I was turned onto Porcupine Tree after reading SO MANY positive reviews of their music. In fact, after learning that Steve WIlson produced BWP, I decided to give them a try. I D/L a few samples - liked them - and bought one of their CDs (Signify). I was instantly hooked. I now have everything they've released after that album. ANd PTree are solidified in the ranks of my fav bands! So far, their new release is the best of the year, IMO (but Ive yet to hear Deliverance).
PTree may be the single most emotional band out there!!!!!
Anyway, I've always had a tremendously wide variety of 'favorite bands'. My all-time favs are (in no particular order):
Sting
Led Zep
Opeth
Depeche Mode
Dead Can Dance
Iron Maiden
Porcupine Tree
Tea Party
Anathema
Rolling Stones
Sabbath
Portishead
Katatonia
In the Woods
Rod Stewart (classic era - 70s)
Aimee Mann
My Dying Bride
the Gathering
Emperor
Pearl Jam