There's a lot of bands, but if you guys are talking more about quality we may have to say that he's right. As great as Oasis were/are, their imitators have a habit of sucking immensley.

Ocean Colour Scene? Boring.
Snow Patrol? More boring, their current hit is milk toast.
Travis? Bo-oring.
Cast? Good straight rock, but obscure and not cool to anyone who looks down on "dad rock."
The Soundtrack of Our Lives? Eh, okay. Nothing exceptional.
Good Charolette? pffffffht.
The Strokes? If your friend isn't one of the legions that hate them.
The Charlatans? Had some of the magic, but not enough.
Kaiser Cheifs? Mediocre
Kasabian? Derivative; Oasis' talk - the walk
Arctic Monkeys? Overhyped; large but young and cultish following

I think the only legit argument you could make is BRMC. Maybe Jet. But since the ace Oasis had was their ability to do good takes on the people they 'stole' from, I think lesser bands imitating the resulting sound is always going to come out as angsty alt rock trash. You may have a case by citing '90s - current bands who were influenced to mix retro styles into their own, but it won't hold up well if someone's just determined to spite them.

Kasabian derivative and Jet not? I like Jet, but what the fuck?

And I doubt The Charlatans were influenced by Oasis, they were band at least 5 years before Definitely Maybe.