Have you watched Baka to Test? How do they compare if so?
They're very different shows with very different tones despite both being rom-coms. They're also both products of their time and the humor that comes from each. School Rumble is a pretty funny show but, and this is a silly thing to say but compared to Baka is true, is much more realistic. It's weird and silly and irreverent but it mostly keeps itself grounded and also uses that to create small moments of drama that build up over time. The humor and build up comes from the characters and focuses on their growth (well...not really) and interactions. I like it (in fact I like it quite a bit) but I find people have a tendency to over-rate it simply because there aren't a lot of great rom-coms with similar tones.
Baka on the other hand is situational and focused more on the comedy with a smattering here and there of romance. The characters are fine and funny but generally fall into their holes with little need for growth because the humor comes from a lack of any progress as well as the situations that come from the archetypes each character fills. Not to say that they aren't funny and the characters aren't cute or fun but they're all pretty much "fuwafuwa character" "sadist character" "pervert ninja" "the third gender" and not much changes ever. So the humor is very much based on what whacky hijinks they get up to that returns them right back to the status quo. Also the setting is your more modern setting which foregoes realism and injects in some LN bullshit about crazy stuff based on a Wikipedia article the creator read and didn't understand one day. Which is fun but your mileage may vary if you look for focus on things that aren't that. As I said before as well, while the "rom" is there, much like many romcoms of the modern day (and even a good chunk of the past to be frank) there isn't much progress because a lot of people think the chase is more exciting and interesting than the catch (spoilers: it rarely is). As a result the show is fun and entertaining but at a different level than School Rumble.
School Rumble is like eating a Lindt Truffle that you forgot about and is a little old but the milky smoothness inside is still delicious and Baka to Test is like cotton candy, just a big ball of sugary fluff.
If you wanna watch a good romcom that focuses more on just two characters and the interactions and relationship blooming between them with a tone of humor, progress and character growth then watch my Top 1 Romcom of all time, Lovely Complex.