Interesting point, I haven't really thought of the concept "casual" as a way to promote games before. To me it instantly puts it in a better light - anything that can make more people find their way to playing games can't be all that bad. I'm just worried that we will end up with something of a gaming "a- and b-list" where games branded "casual" are being looked down on. Especially if they have mostly female players since everything that's dominated by women sadly tends to be belittled.

On another note, the three qualities you mention - mass appeal, to be easy to learn and difficult to let go of - to me they sound like they would be worthwhile in just about any game. Sometimes I wish that mass appeal wasn't as important as the others but I know that in reality it almost always is the most important one.

To achieve the third one - to be hard to let go of - there has to be some depth to the game or it just wouldn't stay interesting. So if any good game needs depth can they really be "casual" in the way we use the word today? I'm not so sure.

But yeah, if it sounds less intimidating there is a point in doing it anyway.

I may have entangled myself in my own reasoning here but what I guess I was trying to say is that simple rules don't necessarily mean that there is no depth to the game. Without any depth at all a game could be fun for a couple of minutes but in my eyes I don't think it could last any longer than that. The depth in Tetris I guess could be finding different patterns of bricks that works better than others, learning to put these patterns together faster than you could before and so on. But I wouldn't really know since I've never been a hardcore Tetris player myself :)

I guess in the end it boils down to a question of definition (how to define "depth"). But I think "Easy to learn but hard to master" like you wrote, pretty much sums it all up.