And I understand that, as a fan of any Space Marine force that falls under the "codex marines" blanket but is not the Ultramarines, it is easy to feel the sting of neglect when the Ultramarines have twenty pages of exclusive content in the codex while your faction probably got a two-inch blurb, a picture of your color scheme in the Index Astartes, and maybe one painted miniature.
But when you look back, historically speaking, the treatment is not so bad. Look at the second edition codex for codex-adherent chapters:
|Mmm, those bright red boltguns...|
So, now that we've established that the Ultramarines didn't just Kool-Aid Man their way onto the scene for the sole purpose of stealing the glory from your awesome homebrew chapter (or any of my three awesome homebrew chapters)... why would anyone like them? I mean, once you get past the Matt Ward wank, they're just vanilla marines, right? They go by the book, so they're lolpredictable, right? Well, not exactly.
There's a reason the Codex Astartes has remained the gold standard of warfare for ten thousand years. That's because it's got provisions for everything. I mean, Space Marines are the guys you call in when everything is already FUBAR, and when they show up, they turn the tide of war. Some people will tell you there's no way a hundred guys can take a planet. Well, that's conventional logic talking. The Codex begs to differ. The Ultramarines are, to a man, dedicated soldiers who have spent decades or centuries fighting together as brothers. They combine the individual prowess and warrior ferocity that makes Space Marines such terrifying foes with the discipline and rigor that changes Imperial Guardsmen from a ragtag bunch of men into the Hammer of the Emperor.
Their style of fighting doesn't have the flashy awesomeness of SPACE VIKINGS. It doesn't have the relentlessness of half-man half-machine Iron Hands or the mystery and enigma of the Dark Angels or the CLEANSE AND PURGE fanaticism of the Black Templars. That's not what they're supposed to do - but the wonderful part is, they don't have to because that's why other chapters exist. The Ultramarines exist to fill one role, and they fill that role very well. They are the gold standard of ass-kicking. When you want to show how awesome you are, you say "better than the Ultramarines."
There are plenty of legit reasons to hate the Ultramarines. If you're filthy Chaos scum, for example, you have a good reason to hate the Ultramarines. If you're some nameless Tyranid beastie who just got dissolved by a bolt shell full of bio-acid, yeah, you have a good reason to hate the Ultramarines. But if you like the Imperium, don't hate the Ultramarines just because they're popular. If you look beyond their overrepresentation in the Codex, there's a lot to recommend them.
Plus, let's be honest, this right here just looks cool.