Very slow. Like 40 hours in gen II to beat the champion, and I think for gen 7 it took 30.
I'll admit, until the time of writing this I had no clue as to what could possibly be slowing me down so much, but besides the fact that I DO check every corner and talk to every NPC, I like to keep all my party around the same level, so whenever I catch a new pokemon I want to use, I focus on grinding levels for it by fighting NPCs while using that mon, which makes fights take a lot longer than they would if I just used my starter to blast through. since it's usually wayyy low leveled by comparison.
Basically I play most fights with a ~10 level difference, and do a lot of backtracking.
Still, those were some fun 40 hours! I guess that's what matters :DDD