Just my opinion 
id say 2, 4, 1, 3, immortal personally =)
Diablo 4 No question in my mind
Diablo 1 It had an ambience and foreboding the others just didn’t quite pull off
Diablo 2 Could swap with D1 depending on my mood at the moment. A great one.
Diablo 3 Hard to even call it Diablo this missed big time for me
God tier:
D2 by long margin but played too much
Ok tier:
D4 still need work but getting better
Trash tier:
D3
D immortal
Not played : d1
D1 = D2 > D4 >>>>>>>>>>>>>>>>>> D3 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>D:I
D1 and D2 are hard to rank imo, both are pretty good, but also for different reasons.
D4, it had potential, maybe it still got some left. But it seems like it is moving in the wrong direction.
D3, well, a disaster.
D:I is an affront to gaming.
id say not having a paladin type class is a bonus. puts d4 on top for me.
For real, horrible class, doesn’t even fit in the game, thankfully nobody wants a holy knight class…
…oh wait!
I would go with:
D2 with Expansion
D2 without expansion
D3 with Expansion
Hellfire
D1
D4
D3 without expansion
and way way down at the bottom: Immortal
I liked d3 before seasons got implemented.
I think d4 will be the same as d3 because of the model.
3 month cycle times forces the game life to be short and transient.
Ive never played d1 or d2 (i own 3 copies - i have unopened diablo battle chests as gifts.
D2, D4, D1, D3
Make an expansion for D2 ;]
My personal list is:
D2
D3 = D4
D1
D Immortal
Diablo 1 I definitely have a nostalgic spot for, but I have to admit it’s a limited and somewhat frustrating experience now-a-days. That said it’s fun going back to the days where game balance just wasn’t really that important and the next game after a failed run you could just find some super busted item.
D2, D1, D4, D3
20 chars 
I never played Diablo Immortal. At first I didn’t get it because it was mobile only. Then when it came to PC I didn’t get it due to the P2W aspect. I read some folks were spending $1,000 to get advantages. I wanted no part of that. How good is it?
i thought we were ranking the depictions of diablo ):
D2 1.08-1.09-1.10 Hail the Prime Evils
D2LOD Runewords ruined balance and made Uniques worthless
D4 It is getting there
D1 It laid the groundwork and was spooky at times.
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D3 ewwwww yuck!
D:I would not touch it.
Diablo 2. Obvious reasons
Diablo 1. The dark ambience of the whole game was great. I remember being scared to fight the Butcher, not because he was difficult but because the feeling of dread throughout the whole game.
Diablo 3. Was boring at first with decent storyline. Reaper of Souls made it come to life. It is good for what it is which is basically an arcade lottery machine where you just destroy hordes in an instant and your screen is filled with loot. Not difficult whatsoever.
Diablo 4. No Diablo.
*D2 it was revolutionary and with LoD almost perfect
*D4 - the genre is old now, lore changed but it felt really good and gets better, hope the don’t do the same as to D3 (see below why)
*D3 was awesome after 10 years a new Diablo in my hands unfortunatly the devs made it to casual or i don’t know how to call the powercreep after seasons got implemented. But before it was also a disaster before loot 2.0. I liked and like it but they did so many wrong decisions to attract “casuals” are new players that they missed a huge oppurtunity to come close to D2, i don’t want this happen to D4
*D1 the beginning. My very first computer game. Played it at my cousin almost a year before D2 release as a kid. Every time i was at her home i asked to play Diablo. Nostalgia kicks in later she gifted it to me and i wished D2 for christmas.
Till today Diablo was the only Hack & Slay series i really like and i play. Tried everything but nothing catched me more like this universe.
D3>D4>D2>D1. Didn’t play Immortal and don’t plan on it.
To add to the Poll which Diablo also had the scariest Butcher? “Fresh Meat!”