Only fun I had with BL2 was playing as Krieg, and that was a lot of fun even if most of what I did was be a burning corpse waiting for a ress.
There was little to no oomph to the guns, and the guns in BL1 had plenty, so they fucked it up. The revolvers in BL1 were sometimes downright obscene in their gratification. I remember getting an explosive revolver at one point, and not wanting to replace it because it meant no more point->MAGNIFICENT BANG action.
I like KF2, but I've often seen it reviled on Holla Forums. Hopefully, an user can chime in on why it sucks.
They've added a bunch of new zeds: 2 clot variants, a stronger gorefast, a super clot that buffs surrounding zeds, and a new boss, Dr. Hans Volter. Whether you get the Patriarch or Volter is random, afaik.
They haven't added all the KF1 weapons so far, but there are new ones, as well as new perks.
The Demolition perk can now add booby traps to welded doors, making them explode when they break.M32 grenade launcher (revolver-like magazine?) is unavailable. Pipebombs as they were in KF1 are also unavailable. You get remote detonated bombs instead.
Berserker can parry attacks now. Some attacks can't be fully parried (mostly certain Fleshpound, Scrake, and boss attacks), but one of his talents adds further damage reduction to his parries. Parrying knocks back the parried enemy.
Support works as a walking ammo crate (minus the grenade) for everyone but the guy playing as Support once per round. Demolitions works the same way, but with only grenades.
New perks, iirc, are Swat, Gunslinger, and Survivalist. Swat uses SMGs, Gunslinger dual-wields pistols and revolvers (can't mix&match them when dual-wielding), and Survivalist is a jack-of-all-trades that can use everything but not as well as a dedicated class.
Levelling system was altered from 0-6 to 0-25, and you get a talent point every 5 levels. Talent points are tied to each tier, so your lv5 point lets you pick one of the two lv5 perks, and so forth. Individual levels aren't as big a difference maker as they were in KF1, and some of the talents award abilities that were available to the whole class in KF1. Berserker getting increased running speed is one of the lv5 talents.