I read at wikipedia that it is JLA/Avengers canon crossover... but is it right ?

Not actually universe vs universe... e.g. - Batman vs Punisher, Superman vs Incredible Hulk... or sth :)

No.

JLA/Avengers was canon due to references on both sides. But DC rebooted, BUT the upcoming storyline convergence implies that pre-52 universe still exist so I believe it's still canon just not for the new 52.

JLA/Averngers was supposed to be canon.

I don't know if DC Vs. Marvel was supposed to be cannon, but I thought it was interesting that Joker made a reference to Batman and Spider-man meeting before saying something like, "Am I the only one who remembers this?" which I thought was a cute nod to a different Batman/Spiderman crossover.

I haven't read those comics in a decade, so I might be a bit off, but there was some conversation along those lines.

No. DC fans would riot if THOR and Cap won a canon fight.

JLA/Avengers was.

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Yeah....pretty sure there's enough references and hints to say it was totally canon. Axis even made an appearance in Green lantern issue 87. Him just being there confirms the crossover is canon. "maybe that guy on the surf board". Gee. I wonder who he could be talking about? (Sarcasm) Spoiler alert. It's Silver Surfer. Green lantern had a crossover with him in the 90s. Kronos and the cosmic egg are mentioned multiple times in the Trinity series and the crossover is mentioned in many characters bios from the handbooks.

@the_stegman: Nah, I don't believe it is - good thing too, as this arc was terrible.

What references there are here and there in various Marvel characters files afterwards are rather oriented towards the Avengers' encounter with the Squadron Supreme (one of Marvel's take on the JLA), which took place in some Avenger issue before (an Annual IIRC), rather than with the JLA - I was collecting both at the time.

No