Casual gaming is really damned by the hardcore gamers nowadays, but gaming really needs the 'find a mechanic that sticks then work it to the bone' mentality Popcap so obviously has. Not saying that I don't like the 'everything and the kitchen sink' approach most mainstream games have, throwing a bunch of mechanics and letting you do whatever, but... well, that's like comparing Airplane! to Psycho. I love Airplane!, it's very fun and always a nice watch, but it's not even in the same level as Psycho. Psycho is actually probing the medium of films deeper, it's setting a bedrock.
Not saying that Bejeweled is setting a bedrock while GTAIV isn't, (though that might be true), but the mentality that advances gaming as a medium comes from that. Gameplay is the language of games.