IMHO, there is no game on kongregate that could not be remake in java (even 1.1
) (NB: I love to play those one), so why developper interrest is so poor ? maybe because :
1 -> when you play a flash game it start smoothly and inside the browser (that's why end user like it).
2 -> IMO, most flash game have not be done by hard "developpers/programmers", the flash studio is great and designer oriented, so game maker are concentrated on gameplay & design and so bring out good gameplay & design
(that's why there is so much flash game and so good/fun gameplay).
nowadays lot of games are made using some kind of studio (flash, virtools, unity, shockwave, wild tangent, etc..,etc...), so maybe if a day a really good studio using java is bringed out story will be different. java need a good hens to be able to make a lot of good eggs EDIT:
unity is very promising http://www.willgoldstone.com/tutorialdemo/menu.html
window/mac/linux and probably Wii ... but that's outside of "casual" more targeting heavier game (sry to be out of the subject...)