I forgot 3 was all vault for it's intro, which yeah that would kind of muddy the waters if 4 just copied that.
I never really understood most of the hate for the intro's of the 3d games, but at the same time I also don't understand why neither Obsidian nor Bethesda ever included a skip intro option for any of their games. Maybe I'm just built different since while they're usually the most boring part of the game, I always make a point to play through them since the game would feel incomplete with out it, and I usually play theses games at least twice a year. Meanwhile most only do like every 5 and they still have time to complain about the tutorials.
At the very least none of them are nearly as bad as the Temple of Trials.
Really? I haven't played any of the TES games beyond Morrowind, and even then I haven't finished it, but out of the 2 FO games I was gonna say 4 had the better MQ compared to 3.
First: I love 3's intro.
But 3 was my first Fallout game so that is definitely influencing my decision there. It may also influence why I place its main story above 4, but I do have my reasons for it.
3's main quest was extremely linear alongside being incredibly short. IRL there's someone out there who only did the main quest and got the shock of their life when the credits began to roll after 7-10 hours, which can potentially become 4 to 5 if you know where James is in advance and beeline for 87 after you meet Elder Lyons. There's also only 2 pivotal choices lobbed in at the end (Modified FEV + send in Lyons) that didn't fucking matter in the original Fallout 3 since the game ended after you activated the purifier.
3's MQ starts off strong but the end is backloaded with a ton of contrived bullshit to push the plot along in the specific way Bethesda wanted. Autumns ambush of the player in 87, Eden somehow being convinced you'd do his bidding after his people killed your dad + infamous "Kill yourself - NOW!" speech check + spontaneous Enclave civil war - all just to allow the player to escape Raven Rock. It's
dense with dumb, but it does by quick.
This is alongside the purifier choice requiring abandonment of all logic because you can't send anybody immune to radiation in the original, essentially making your self-sacrifice retarded are a result of fucking peer pressure lmao - it's especially egregious since if you're good karma your options are Fawkes (super mutant), Cross (Brotherhood lady people forget exists), and the ghoul from Underworld who doesn't need a karma check to have a companion. Chances are, you're going to pick the OP mutant or the guy who requires a big investment to acquire in the first place. If you're evil karma, the ghoul is still one of the better companions as the easiest method to get him is to murder another character which should be a piece of piss if you're evil anyway. Chances are, you're going to end up in a situation where the logical choice is to send in the guy immune to radiation and the game chastises you for not throwing your life away.
3's main story suffers from some extremely dumb decisions in the last 3rd, which stick out more by virtue of appearing at the end and being so absurdly stupid that they are pretty hard to defend. However one of its flaws helps to ameliorate this: It's also very short. If you skip the treasure hunt for your dad you cut the quest in half.
Regarding 3's cringe, I'd say it mostly concentrated in 3-Dog because the "good fight shit" is genuinely vague wishy washy shit that is just as cringe IRL when hippies do it and it's equally cringe here. Though you wanna do his quest if you want map-wide coverage of GNR - I can't not go through the Wasteland without Mighty Man, man.
And after all that shit, I still like it. I think it has a strong beginning (Vault intro (which I like personally) + hunt for Neeson itself having you run into a lot of interesting locations via diegetic means), middle (initial Enclave conflict + Brotherhood intro + excursion to Vault), and the end is where the dumbest shit is but fighting through Raven Rock + Liberty Prime and the fight towards the Jefferson Memorial are all really strong moments to me that 4 doesn't match in its final act. The closest to a good finale is if you bring down the Brotherhood since the Prydwyn's burning descent is a more interesting and striking visual than a large mushroom cloud. Unfortunately the Brotherhood has the best main quest path narratively speaking and in terms of set pieces, so you don't get to see it unless you go full retard (Institute or Railroad) or a bit dull (Minutemen).
How did my post shitting on Fallout 3's MQ somehow equate to it being better than 4's MQ? Here's a secret: my first playthrough of Fallout 4 was in the release month, totally blind. My chosen faction?
The Railroad.
After my first playthrough didn't play 4 again until after 2020.
" I was wincing the entire time I had to interact with any of them. I didn't know the Minutemen were a faction and I resolved to finish the RR's quests first and then do the based Brotherhood. Passed the point of return and suddenly I was watching the Prydwyn burn up. 
