I'd say 2 and 4 were just as bad as 3. No Disgaea has been good enough to match the first plot-wise, with DD2 being the closest in the sense that a retarded kid on ground level has a better chance of reaching the top of the Kilimandjaro than the three crippled AND retarded kids.
Disgaea 2 has Hanako being literally cancer, Taro, Yukimaru and Tink being worthless, Axel being somewhat okay and Adell being boring as hell. It also raped the D1 trio so hard they didn't even completly recover yet. Zenon was a bad villain because he spent the game being tossed around, first by Etna then by Rozy. A level ~100 final boss isn't very impressive when we got tossed around by a level 1000 Etna in chapter 2, (not including level 1200 Laharl and Level 1500 Rozy).
Disgaea 3 was holy crap bad. It went for humor and mostly failed. The school part was interesting, but then they killed it by having it shoved down our throats. Beryl also got pretty old really fast, her minions were never funny, Sapphire was pretty much a tool for Almaz and Champloo relied on his quirks too much to even be considered a character. Mao was okay, if only because his character development was so cliche it was impossible to mess up, same for Almaz. Bright side: Aurum was a pretty good villain, if not the best in the series. He had interesting motivations, his actions made sense and his reveal is probably the only real plot twist in the story.
Disgaea 4... ugh. Fuka and Desco dragged down an already mediocre story down to atrocious levels. Half the early game chapters were chasing down Axel, who got the D1-trio-in-D2 treatment. The other half was Emizel's part of the plot, which was okay. It was so okay I just played it with no complaints and pretty much forgot about it afterwards. Val played the mentor role to Emizel in what was probably the best character interaction in the story. Then the second half is chasing around Nemo. Oh boy. Not only do we have to follow him around, foiling stupid evil plot after stupid evil plot, but the have a peanut gallery following us around, making useless comments after every plot twist. "Gasp! Something happened!" "Hey, I got a snarky comment!" "I got a snarky comment for big sister's snarky comment!" "You are both idiots." Count every time that happens. I don't even need to name the characters. You probably read the comments in their voices. Nemo, in the meantime, never goes past the "angry guy" level of villainy, and he doesn't even go all the way. At the last second, he decided "Oh I don't wanna be a villain" and pussies out. He needs a fucking magical power to take him over before he can actually be a proper final boss. Whoop dee doo.
Disgaea D2 had good parts. Shocking. The Krischevskoy group are interesting villains because the feel complete in character and motivation. The want to control the netherworld so it stay as good as it was before, but they have huge nostalgia googles and they're not actually all that competent. They have their failures, they get called out for it, and they have retorts. They're right to say that Laharl hasn't earned their respect yet, and both sides mature and reach a proper understanding of each other. Also, their post game chapter actually made me laugh, in a good way. The flowers on the netherworld plot was a good setup, and Xenolith had some interesting points. He looks like the cliche mysterious guy, then next chapter he goes ahead and reveals half his motivations before we even know he's a villain. That's almost refreshing. His interactions with Etna during that chapter are also really good. He teases her with the information, she doesn't take his shit. he reveals it, she still doesn't take his shit. That was great. It felt more real than if Etna had accepted it. She decides she doesn't need a brother, he's sad, but he accepts her decision. Then he goes ahead and becomes a garbage villain anyway, oh boy. Not only are his justifications weak, not only does he fall squarely into the hole he had avoiding in chapter 6, but just like Nemo he pussies out of being the final boss. Not a good trend. But since I liked most of those things, why did I say the story was garbage?
Well, there's mostly one thing I haven't mentionned yet, and at this point you proably already know: It's Sicily. Holy shit not only is she a complete waste of time a la Hanako, but she's blatantly pandering to the cute little sister crowd so much it almost vomit inducing. This is from someone who usually hears the whole lines being voiced out before moving, I had to skip her lines just to avoid having to listen to the garbage she's spewing out. After chapter 6, when everyone accepted that Etna couldn't really think of Xenolith as her brother (for very good reasons), she goes ahead and farts out "But how can someone not love their Onii-chan!". Wow, fuck you Sicily. Her whole character is that she wants to be with oniiiiii-chaaaaaan, and that she kinda likes Prinnies. That's the shallowest out of every character in the series. Even Fuka has more character than that. Even Taro and Hanako do. So if she's worthless as a character, how is she as a plot device? The answer: worthless. She's there to assure us that Laharl really can feel love and that his tough exterior is just a facade, which would be interesting if we didn't already have a whole game and a whole other character dedicated to that. Sicily could be completly removed from the story with no ill effect. As it is, she's just fighting in a battle that Flonne already won back when the series began. Actually, she's not worthless, she's lesss than worthless. She makes other characters worse just by being near them. She eats up Flonne's relevance and in the last chapter, it turn out Sicily was right and Etna DOES love her oniiiiii-chaaaaaaaan. Laharl is the only one relatively unscathed, because the things Sicily did the him were things that were already happening to him... because of Flonne.
so Disgaea D2 would've probably gotten a "good" for me if it hadn't been for Sicily. She's already terrible in chapter 2, and that's before she reveals the true extent of the monstrosity she is. I would say story-wise, it goes D1 >x10k DD2 > D4 > D3 = D2
also, you fuckers posted like 12 times while I was typing this so its not actually relevant anymore.