1 is good, 2 is good and is one of those iterative "we're directly building off the previous game" sequels, and Off The Record is a remake.. thing of 2, and it irons out some of the game's issues while also providing a sandbox mode for you to play around in. 2 and Off The Record both have co-op, and honestly some of the bosses feel like they were designed with co-op in mind because they're pretty rough running solo. they're challenging games, and i feel like especially with bosses it becomes clear how clunky you actually move.
3 dramatically reduced the timer element (now you just get a week to finish the game instead of events having to happen at specific times) and put a bigger emphasis on exploration. while i guess the first two games were open world titles, 3 really leaned into the open world aspect and gives you a whole city to poke around in, and that's... neat? i guess? i don't know, the grey cityscape of Not!LA doesn't really do it for me. it feels really subdued compared to the weird heightened reality of the first game's massive sprawling mall and the second game's casino oasis.
4 is.... hrmm. as someone who has no real attachment to the franchise, you could very well enjoy 4! for like 8 bucks or whatever it is on Steam right now, that's probably fine! it was a very hastily made game, on what i assume was a fairly tight budget and time table. the writing is annoying. the sound track is annoying (they recorded A Lot of original christmas music for this game, and all of it is very competently executed, but oh my god does it grate). a lot of the fun little details and side stuff you could do in the old games is gone. there aren't a lot of cutscenes, instead stuff plays out in game, and it's kind of annoying because frank will comment on stuff but the camera won't actually swing around to show you what he's commenting on.
they did some updates after it was initially released to add in actual survivor side quests (there's like... seven), so i guess that's nice. the maniacs also got unique weapons that they drop when they're defeated, so that's... slightly better than the Literal Nothing they were when it was initially released.
i think dead rising 1 had the strongest story, for what that's worth.
a note on the concept of "do they hold up":
revisiting the series in 2020, there's a lot of stuff that's maybe Not Great, From A Representation Standpoint. 4 is a lot better in this respect, and even though this was a choice the dev team specifically made, you kind of also get the sense that it would have been a lot worse if they had had proper psychopath intros and outros.