I've been gaining interest in the JVM for gaming lately, because of sheer technical superiority:
- It's the most mature, stable web-capable gaming platform around. Attractive plugins like Unity, InstantAction, etc., come and go, but by being extremely proprietary, and not getting a lock-in boost like a Microsoft bundle(which is what Flash got early on), they are declaring themselves disposable and hence are likely to lose long-term staying power.
- Huge quantity of libraries, huge tool infrastructure, most low-level development issues have already been encountered and resolved.
- Attractive modern languages(take your pick of Scala, Clojure, Groovy, and many others)
- I'm sick and tired of Flash's sucky, almost-good-enough implementations of everything.
I think the main thing keeping me from going that route
now is the lack of a marketplace like what has emerged online for Flash. But that in itself seems to be a chicken-and-egg problem - Flash portals first came about because Flash started from a media-centric standpoint, making videos and animations with some interactivity, and they gradually branched into games as the support appeared. And now the situation with Flash is such that all you have to do is send up a game through MochiAds, and even if it's a really terrible game, it'll get at least a few hundreds or thousands of plays without any real legwork on your part. It's a very powerful way to find your audience, and there's
nothing else like it - the "App Store" type of model is less egalitarian and more open to payola schemes. Hence the dilemma I face in Flash vs. JVM.
There are definitely examples of successful games for the JVM, small and large, but it's kind of depressing how almost any search with terms like "Java games" essentially sends you to student coding projects. The only prominent portal I can think of that hosts Java games in quantity is Yahoo! Games. And they're casual-games oriented, which indicates that we are in a technical Bizarro-Land: the performance-demanding, action-heavy stuff with physics and 3D and other cool tech is getting squeezed into Flash so that people on Kong, Newgrounds, and 1000 other sites can play it, while the relatively lightweight stuff that is reliant mostly on sparkly effects and good graphic design gets made in Java.

(Although, Kong did make an exceptional case of allowing Runescape to run its Java app in an offsite frame; that's a start.)
But it leads me to think: How can I help foster a JVM-portal market on my own and get that same marketplace benefit while using the better platform? games4j looks like exactly what I want to see, and so does GameJolt, but we have to see a zillion such sites. But I think that if we can make games that are really strong and are monetized with similar methods to Flash, the existing Flash-centric sites will start to treat both platforms equally.
When I make my own games, I am perpetually keeping my eye on ways to make the creation process faster and easier; I think that a Game Maker type of program with an engine targeting JVM would be a huge hit and support the above goal. And I have a good shot at pulling it off, too. Gradually, by solving real development problems day-by-day and observing how others do so, I've resolved a lot of the conceptual grounding necessary to make an entry-level system that's truly useful for nuts-and-bolts gameplay tasks. When I wrote out the road map to actually implement it on my own, though, the ballpark estimate was two years of work, including two game projects to test the system in the fires of "real development."
So that's a long-term thing. It'll be open source, of course. And in the meantime, we can always fall back to business models based on "traditional" product marketing techniques. Whatever those are.