Popular and casual indicate similar things, but cannot be used interchangably.

Halo is a revolutionary moderate (not casual or novice level) shooter. Any casual player who plays Halo and does well or excels is no longer a casual player. A casual player indicates this:

The player doesn't spend a lot of time playing games and doesn't care to understand complex control schemes. They usually tend to hate having to learn how each button on a PS3 or 360 controller relates to a character. They just want to pick up and play. Period.

"Casual gamer is a loosely defined term used to describe a type of video game player whose time or interest in playing games is limited compared with a hardcore gamer. Casual gamers can conceivably consist of any people who show more than a passing interest in video games, therefore it is difficult to categorize them as a group. For this reason, games which attempt to appeal to the casual player tend to strive for simple rules and ease of game play, the goal being to present a pick-up-and-play experience that people from any age group or skill level could enjoy." -Wikipedia

"A casual game is a video game or online game targeted at a mass audience of casual gamers. Casual games can have any type of gameplay, and fit in any genre. They are typically distinguished by their simple rules and lack of commitment required in contrast to more complex hardcore games.[1] They require no long-term time commitment or special skills to play, and there are comparatively low production and distribution costs for the producer.[2] Casual games typically are played on a personal computer online in web browsers, although they now are starting to become popular on game consoles, too. Casual gaming demographics also vary greatly from those of traditional computer games, as the typical casual gamer is older [3] and more predominantly female,[4] with over 74% of those purchasing casual games being women."- Wikipedia

This is about considering it casual, not that it is. And if you've paid attention to fanboys for the last ten years, you would know they don't care about correct labels.

I understand you....trust me.

Pac man came at a time when gaming was nowhere as big as it is now. Pac man was mainstream, but it was also a casual title with various difficulties as you progressed. It had a pick up and play style. This doesn't mean that casuals had to finish the game tough. Wii Sports is an evolution of what Sega pick and play arcade games we're trying to accomplish with casual arcade fans and movie goers. It's good to see that at least Nintendo has those pick up and play games on their system...one of my old favorites being the House of the Dead series.

Anyone can Edit wikipedia.

Casual and Hardcore doesn't mean anything, they are false concepts, illusions or just really good viral marketing. It's not the games or the players that matters. It's how the games are played! I, a PC RTS player consider all console games casual. (with some very few exceptions......very few)

Gamers are too complex to just say "Oh those gamers are so casual" or "Look at that game! IT'S F***NG HARDCORE!"

You just can't look at stuff black and white. Even counterstrike is played casually (Although the game is more "hardcore" than any console game will ever be).

Back in the day the shift from the SNES generation to the Playstation generation brought in a new wave of gamers who had very different values when it came to games. Rather than wanting a challenging games that required hardwork to master, many of these new gamers were buying games that were more cut-scenes than actual gameplay; and a large portion of the new audience was people who had previously shown little interest in videogames, and made fun of or bullied the kinds of people who played videogames.

I always find it interesting to read people who are so critical of "Casual Games" or "Casual Gamers" when they don't realize that (roughly) a decade ago they would be (basically) the "Casual Gamer" and every game they think is so "Hardcore" would be considered a "Casual Game" that many of the elitests were claiming was ruining the industry.

Games like Pac Man, Pong, and Space Invaders were breakthrough titles on platforms people played games at, which was arcade at the time.  I think you did hit the word that fits this "mainstream".  "Mainstream" is where casual and hardcore meet.  Some mainstream is more casual, while others is more hardcore.   Mainstream games get their own products outside of the videogame business, like beverages and breakfast cereals, or they at least appear in mainstream TV ads.  Examples of this include the likes of Starcraft in South Korea, and World of Warcraft here.  Such a breakthrough leads some to say a game is "overhyped" because of the mainstream appeal.

Mainstream games act as ambassadors for the videogame business. 

I think of an interview with Nolan Bushnell regarding the nature of the videogame business and how he said the lack of mass appeal arcade game designs hurt the business.  I believe the Wii has brought this back, except now you find that core players, married to their gamepads, are upset at all the newcomer noise.

I wonder why they have worldwide Guitar Hero and Rock Band tournaments? Those games are nowhere near hardcore... Just because your game plays in world-wide tournaments, doesn't make it automatically hardcore... If over half of your userbase has the game (HELLO, HALO 2 at around 60%), then your game cannot be classified as hardcore...

UFC is a sports game. Like it or not, sports games are very much casual... Madden has a learning curve as well (which is why I suck at it)... However, if you know enough outside information about either sport, then you can probably pick up and play the game moderately well (which is why my brother is moderately good at it)... No, you're not going to beast through a bunch of people who have had the game for 3 weeks, but you will do acceptably well... Similar to Guitar Hero, you're not gonna pick up the guitar and start shredding away Expert levels if you've never played... However, If you've ever played a guitar, or watched someone play, you'll probably be able to beat someone who has never heard of the word "Guitar" before.

The fact that you said No More Heroes isn't core is bizarre... That game has core written all over it... Then you go and say another game like it is core? Where is the logic?

Arcade-made games? I think you are talking about fighting games... I had never played Galaga before in my life, and the first time I played it (I was 8), I got up to level 10. Obviously, that's nothing really good (Level 50 with just 1 quarter nowadays), but for a first time, I didn't "Fail" at it... Arcade feature tons of "casual" games. One example: House of the Dead. EDIT: 1 - 4

This confusion over "casual" games and "hardcore" games is ridiculous.

The last post mentioned HotD being casual. Pardon me while I puke... Excuse me?!

Casual games are ones that are easily accessible, quick to learn, quick to play, and appeal to large audience. You can't tell me that shooting zombies appeals to a large audience. Also, to be good at it you need to invest serious time, and have quick reflexes, thus meaning it's not very accessible.

Just because a game is simplistic doesn't make it casual!