I would say yes, and much like Halo or Call of Duty, it can be played casually as well.

For me it is.

Put a "hardcore" elitist Pokemon player against a pro in FPS. They will cry for their mommies on the mic.

 
BTW, I'm asking if pokemon is hardcore because I'm playing pokemon black, I'm in the fifth city now and I'm really enjoying the game. It's kind of a reboot, old school addictive pokemon.

the beauty of pokemon is its for both

you can play casualy for fun 

but if your really into it you can go into IV and EVs and the game gets as hardcore as can be 

so

yes

but 

no

as has been said it depends on who is playing it and how. Just like just about every other game, very few games can't be played in a hardcore way. And most of the of the games that are considered "hardcore" can be played in a very casual way. The distinction is nebulas, inexact and pointless.

Pokemon is exactly as hardcore as you want it to be. That's why HeartGold and SoulSilver include the Pokeathon and EVs simotaneously.

bleh any game can be hardcore. And all the annoying kiddies always play the most popular hd game, which sadly happens to be halo atm, but thankfully black ops will come out soon and the kiddies will move on to that and I'll be able to enjoy halo. But ya its not the game thats hardcore, its the player. Except maybe some ridiculous game like this (I know its old) http://www.youtube.com/watch?v=sQZuidKexBQ

Go to any guys college dorm and you will see how hardcore it is.

This pretty much sums it up:

WTF!!! I'm in High School and Pokemon is the shit! And I'm one of the reasonably popular guys.

:O Your school is awesome.

(That wasn't the case in my high school. But in college... everyone was playing Pokemon. It was redonkulous!)