I enjoyed the first half of sixth edition. It was quite good to Guard players that didn’t want to run Mech Vets *ALL THE TIME!*
For me, 7th made me actively consider selling my collections, and got me trying other game systems, notably WMH. Had my group been more willing to give it a go, I’d probably be playing that as my main game.
As it is, the lustre has worn off of 8th for us. We’re playing Magic these days as our main game. I play the odd game of Kill Team, and I enjoy that much more than typical 40k
I just wish WMH was more accessible... but now I really wander from the OP
. As much as it pains me to say, I really miss the old deep strike rules. As a Guard player.
5th edition was a very solid ruleset but suffered badly from badly imbalanced codices, with each new army being more unfair than the last.
6th edition tried to start selling people on collecting multiple armies and was mostly successful, but had a few serious problems with the core rules that gave major advantages to armies which could exploit them. (The introduction of flyers, in particular, turned the meta into a haves-and-have-nots system where anyone who could spam flyers would crush anyone who lacked AA.)
7th edition was a better basic ruleset than 6th, since it was very similar to 6th edition but with more refinement (and one of the edition changes where there were the fewest differences from one to the next,) but it suffered massively from supplements that tried to fix problems and consistently made them worse.
Of the editions I've played (excluding 8th), I think 6th was probably the worst ruleset, but had the closest thing to balance because the codices were the least out of whack. 5th was definitely my favorite to play.