Back when I first bought a Xbox 360 the marketplace was filled with silly arcade games that I primarily used to waste time while other videos or games were downloading.  It was all about the blockbuster hits and massively entertaining games I paid $60 for each month.  The $10 games I bought every few months or so were just time killers in between short periods of boredom or uncertainty as to what I wanted to play next.  However, the XBLM has become a haven of video game greatness and I would argue that some games you pay $10-$15 for are more worthwhile and fun than the games we so readily pay big cash for.
 
Stacking, Torchlight, Castle Crashers, Shadow Complex, Limbo, Pacman CE: DX, the list goes on and on.  These games are cheap but they pack hours and hours of originality and creativity into their tiny non-existent packages.  For example, Singularity is a fun shooter in my mind.  It has a good feel with it's shots and the time manipulation is entertaining for both combat and puzzles.  After about eight hours the single player is complete and...you're done.  The multiplayer isn't for everyone, nor is any multiplayer game for that matter, and there isn't  much left to do once you beat the game.  Singularity came out at a starting price of $59.99 and had about 8-10 hours worth of single player game time, while games like Torchlight or Castle Crashers cost around $15 and have easily four times as much content in them.  
 
Then there's the originality of downloadable games.  Not to pick on Singularity, I really enjoyed it it's just fresh in the brain, but it is comparable to a laundry list of videogames and videogame concepts.  Time manipulation has been done before and so has atmospheric first person puzzling/shooting.  When is the last time you played a Russian stacking doll game?  The art design, the puzzle design, and the humor of Stacking sets it apart from anything else on the market, be it retail or downloadable.
 
It's becoming readily apparent that downloadable games in general are filling the niches that big budget games can not. It's like indie music, Animal Collective doesn't sound like anything you're likely to hear on your FM radio stations nor will their albums make as much money as the new Lady Gaga album.  We call them "Arcade games" "downloadable games" and other ambiguous titles, but in reality these games are just that...games. 
 
Double Fine recently became a behemoth, no pun intended, in the downloadable game sphere.  With the releases of Costume Quest, Stacking, and the soon to be out Trenched they are taking what is fun about game development and making it a reality.  After casually talking to Tim Schafer at PAX East it's apparent that they don't sit down and say "what will make us tons of money" they instead ask "who has an awesome idea and how can we make it real?" You can be walking around in a mobile trench killing TV monsters or become a knight taking down barbarians to save a princess, why limit yourself to wartime shooters?  
 
When it comes down to it I guess it just feels like imagination is being held onto by a select group of individuals.  These are the people who make games fun and unique and make people say "holy crap you have to play Limbo".  I don't expect this x factor to sink into mainstream big budget games, I just want it to stay alive in the downloadable sphere of gaming. Basically, if I see a $15 Call of Duty game...I'm out.