IMO theyr is no casual or hardcore game, only a casual crowd and hardcore crowd.

I consider myself a hardcore gamer, but recently ive been playing alot of Mario Kart7, MK is neither a core or casual game, but it appeal to the casual fanbase. It also appeal to alot of core gamer.

So games like mario and nintendogs rly appeal to the casual market, but theyr is no doubt that ALOT of hardcore gamers play mario and pokémon so they are NOT casual games, they are simply games that appeal to a wide crowd.

I wish we could stop saying ''this game is casual'', srsly saying that smash bros is a casual game simply because ppl of all age and sexes can enjoy the game is plain stupid. The fact that everyone can enjoy the game doesnt make it a casual game, it simply makes it a darn great game.

To give a serious answer to this, I believe that all of the games listed above could be considered either with the exception of Monster Hunter.  The only reason that I would classify Monster Hunter as an all out "hardcore" game is because you have to put forth a lot of hours and effort to get anywhere in the game. 

The other games can be enjoyed a lot by someone that plays them for only once and for short period of time, but all of the above would take a borderline maniac to master.

Examples: 

- I knew a guy that would not consider Guitar Hero to be completed unless he got 100% on every song on every difficulty.  That's pretty hardcore.

- Getting a 9999 VR or a three star ranking in Mario Kart is pretty hardcore.

-  Beating Super Smash Bros Brawl's Boss Battle mode on intense is another insane thing to do.    

This is basically my opinion:

Must be that time of year again...

There are casual games and casual gamers and there are hard core games and hard core gamers.

Most games are just games though and most gamers are just gamers.

Sometimes you can play a casual game hard core, sometimes you can play a hard core game casually.

Playing hard core is pretty much defined as spending lots of effort and time. So a game that has a hefty learning curve or takes a lot of time to complete or effort to master would tend to be hard core. The flipside though is that hard core games can often be pretty niche with a few exceptions (mainly from lots of people being trained on prior games, continually building up that segment of players devoted to the specific skill of playing that one game). Often the burnout is high.

Whereas a game that has little depth but lots of breadth (or vise versa) might be pretty easy to pick up and play. Often friends and family can come together to play these game with little effort and a pretty level playing field (mileage can vary with age). The flipside though is that lots of players can put in an exceptional amount of time playing these games (sometimes many times more than a hardcore game) because of ease of picking it up and playing a few rounds of the game. Often the burnout is low.

None of the above _really_ matters. Lots of players have lots of different preferences.

There is no such thing as a casual game or hardcore. There are games that are aimed at people who play games CASUALLY, like Just Dance and Nintendogs, low stress, little skill involved, games that dont require hours of your life. Now you can play those games hardcore. You can play JD for hours everyday. However, realistically speaking I bet the vast majority dont do that, they only play when there are people around. On the other end you have a Skyrim, that has hours of originally content, you could play that casually as well. A few hours every other month, but who does that.

None of the Mario games are really casual with the exception of the parties

There's no casual/hardcore. It's more like mainstream/hobbyists.

There was a time when many games were designed to be easy to learn and play, and balanced to allow some progression without too much discouragement. Some were even designed to not alienate certain demographics, such as women. These games were everywhere you went and only cost a quarter to play, giving a few minutes of distracting fun.

These games also sported the precursor of achievements with high-score tables. But I doubt anyone would think early 80s coin-op games were casual.

It's not all black and white. No game is entirely casual or entirely hardcore. Most game have casual and hardcore traits. Here are some of the traits that help define casual/hardcore games.

- Games that are accessible to a mass variety of peole are more casual than games directed at a smaller, more specific demographic.

- Games that are easy to learn & master are more casual than games that are difficult to learn & master.

- Games that are focused on quick, pick-up & play sessions are more casual than games focused on long, deep sessions

- Games that are developed by Sony are more hardcore than games developed by Microsoft or Nintendo.

I'm sure there are more traits that define what's casual & what's not, but I'd say this list covers most of them

Something like Just Dance 2 is considered casual and there's really no debate about that fact.

List of games from most casual to least casual IMO:
Guitar Hero/Rock Band
Mario Kart
Mario (platformers)
Call of Duty
Madden
Smash Bros.
Halo
Grand Theft Auto
Uncharted
Zelda
Gears of War
Street Fighter
Final Fantasy
Monster Hunter