Okay, the only real Irish hero I can think of is Banshee (and Siryn, his daughter). Then there's Captain Ireland from Ultimates, but he hardly did anything. I've always liked Sean Cassidy, and not just because he's Irish. He had a cool power, and he was one of Generation X's teachers. Because of that series, he was easily one of my favorite X-characters. Plus his toy was cool because he had a whistle in his chest! He wasn't used much after Generation X was cancelled, and now he's dead. Dead, I tells ya, DEAD! Argh! It's not like they were using him much anyway, but he'll be missed.
So, uh, Irish heroes. Hm. Yep. Well, there's always Angel. Liam. Eh, he's an entity all his own. Cuchulain was on Gargoyles. And then there's Miles O'Brien. I just started season 4 of Deep Space Nine today. You know what? This sucks!
Just look at Wikipedia's list of fictional Irish people! It's pathetic! I guess what really bothers me is that you don't really know what heroes are Irish American. African American heroes are obvious, but Irish? Not so much. Unless you have a last name that indicates it like Spider-Man 2099 (O'Hara) of Plastic Man (O'Brien), white heroes are just white. To be an Irish hero, you actually have to be born in Ireland and have an accent, being of Irish decent doesn't mean much.
White people in America tend to mix together, so people will end up part Irish, German, Italian, whatever. Not that that's a bad thing, I'm just saying, when it comes to fictional characters, if they're white, their background can just be ignored.
Take Batman for instance. I'm pretty sure he's Scottish-American (I remember this mini I never read called Batman: The Scottish Connection). Who here looks at Bruce Wayne and sees a Scottish American? Is Batman categorized as a Scottish American hero? Look at all the actors who've played him, did they get Scottish American actors? Can anyone even tell? Does it matter?
In some cases it matters. Getting back to the Irish thing, I think Peter Parker may be Irish on his mother's side? I'm not certain. In Paradise-X (an alternate future, doesn't count), they showed Captain America visiting his relatives in the afterlife. So at least in that case, he was descended from Irish immigrants.
You know who's cool? Green Lantern. Kyle Rayner. His mother is of Irish descent and his father is of Mexican descent, so he's half Irish like I am. That's pretty cool. And thus I end on a positive note without even once mentioning Bullseye. D'oh!