- some games have interesting scoring systems (involving chaining enemies, chaining medals, staying alive with maximum bomb capacity, collecting hidden point items, clearing the stage without "options" -- pods. Yes, Varth, I'm looking at you >_< --, combining medals, damaging enemies with bombs instead of normal shots at the right places.. enabling hidden boss battles from where you can obtain more points, destroying enemies which in turn either destroy the bullets around them, or cancel the bullets that they've fired for massive
damage points, using Reflect Barriers to turn reflected enemy bullets into point items as they hit enemies) that make you want more
- some games have somehow more interesting stages than Touhou do (some of Varth's stages demand my awareness and also have a fitting bgm, for example, in stage 12
http://www.youtube.com/watch?v=CEJnAUgZRhM ; I'd say that you must play this stage and others such as 6, 9 and 10 to feel what I'm trying to express. For those who don't know or have played Varth, the enemies can come from the sides, or from behind, and
may will point-blank you most of the times if possible; it also encourages active bombing, since bombs refill themselves after a time), you have to move yourself more, either to damage medium/large enemies that appear on the screen, or to hit "popcorn enemies", or to avoid incoming bullets while you're busy with something else (collecting falling/grounded medals, buying yourself time to recharge your Reflect Barrier, or refill your bomb meter -- like in Varth ^^ --, etc.)
- as you progress in most games, the stages become more fun to play, and you want to play them again and again, and see how far can you get in the game (even if you've seen the later stages on youtube or reached them yourself).