Getting through ME (1) when playing the trilogy is a chore

ME1 is a short game. Just do the main missions. That's all. That's what I do. I do as little as possible to get through the game.

20 hours? I complete ME1 in about 4 or 5 hours without rushing myself.

The reasons for replaying ME1 in several different ways are imbedded in how those differing decisions impact (changes dialogue) in ME2 and ME3.  You can option to not recruit Garrus or Wrex, you can opt to shoot Wrex or not, you can opt to keep several minor characters alive (Fist, Helena Blake, Toombs) or not.  Within ME1, you can opt to select 3 different backgrounds and 3 different psych profiles.  The backgrounds each unlock a different mission and the psych profiles impact dialogue on 3 other side missions in the game.  You can do the game as a male or a female and each gender can romance a different character (Kaidan or Ashley) and one "joint" character (Liara) or romance no one.  All in all, I would say there are clearly more than 2 ways to replay ME1... and each will set up a different sort of playthrough, particularly in ME3 (but also to some degree within ME2).  ME3's playthrough will be very much affected by the decisions made in both ME1 and ME2... particularly when it comes to which characters the player decided to have survive or not survive; and ME2 gives the player direct control over the lives of the 12 people in their squad.

That's absolutely fine.  I like tracing the all the differences through all three games.  I don't play on PC, so I can't just toggle the flags and I found the import comics pretty inadequate and they seem to create some issues on my system as well.  So, I pretty much have to replay at least portions of ME1 to set up those different scenarios.  I do not, however, replay from ME1's beginning each time.  I make saves at choice points and replay only from the point forward where I made the choice I want to change.  For example, changing whether or not the council lived only requires replaying the very last part.

I find that a bit hard to believe. ME1 has 7 main missions: Eden Prime, Therum, Feros, Noveria, Virmire, Ilos, and Citadel. That's not counting all the talky stuff on the Citadel before you get Spectre status and of course companion dialogues between main missions. I don't see how you can cover all that in 5 hours. Sure, if you skip absolutely everything, including conversations, I guess it could be feasible, but what's the point of such a playthrough.  

I believe the record for a speed run without using any glitching is 2 hours and 46 minutes (warning - the single video below is the 2:46 in length):



So, 4 or 5 hours doing main missions is believable... but it does involve skipping the dialogues... which doesn't work for me since my reasons for replaying is to trigger and hear different dialogues and see different impacts.  If I want to replay a game with the same story every time, I've got any number of shooters in my game library.

Fair enough. I'm a narrative/dialogue/RP/worldbuilding junkie though.  I am addicted to talkiness in my games. I could never skip conversations!

I have killed Wrex on Virmire and don't cure the genophage. When I playthrough ME1 quickly, I avoid recruiting Wrex. It adds time.

I can still get a paragon, happy ending even when not curing the genophage.It's not that hard.

My current playthrough admittedly started from ME2 while using Gibbed Save Game Editor to tailor what happened in ME1. However, I generally like starting from ME1 because it affects tiny things down the line, things you said or didn't say that save editors don't always get. They don't affect much of anything except maybe as a reference from a character. It adds depth to the game that's absent by starting in ME2 or ME3.

For example, Dr. Michel. I always meet her in ME1 when recruiting Garrus. Yet, if I start with ME2 or ME3, the game assumes I did not meet her and we're introduced for the first time at Huerta Memorial. It's a small thing, but there's dialogue specific to having met in the past that isn't there if you didn't play ME1. For me, that's what role play is all about. Why miss out on it?

Everyone plays according to his or her own preferences, of course. That said, I admit I'm having trouble understanding what walking through airlocks, having ladders instead of elevators, and choosing Mako or going on foot inside obvious driving-friendly zones have with role-playing.

Most of them, yes. Saving before trying each is part of the annoying. By contrast, I like the mini puzzles in the second game, particularly the script fragments matching.