http://forums.hexus.net/pc-gaming/23...ing-isaac.html
both The Binding of Isaac and Dungeons of Dredmor I'm greatly enjoying, even though binding of isaac is insanely hard and I've not got past the 4th level yet, both have a lot of replay because levels are randomly generated.
Also to the list
World of goo
Minecraft
Death Spank (not a great deal of replay in death spank but I found it a lot of fun if a bit easy)
Gattling Gears (twin stick shooter game, great fun, looks great, but again limited replay)
If you were a fan of the old x-com games then xenonauts is one to keep an eye on
http://www.xenonauts.com/
I'd also checkout Total Biscuit's
WTF is . . . channel on you tube
http://www.youtube.com/show?p=vVuDo8ku4PA
There's some major releases but the majority of titles he looks at are all indy
Some which look great but I've not personally played
The Unstoppable Gorg - a tower defense type game, slight twist you cannot create paths for the enemies but have to adapt your tower positions to the enemy paths
Bunch of Heroes - twin stick shooter, nice comedy world, online co-op
Cthulhu Saves the World - old snes style rpg (made with rpg maker
AFAIK) lovely comedy to it.
Magicka - looks great, not sure if that twin stick, but it's got a really intresting magic system and online multiplayer co-op.
Super Crate Box - old school single screen arcade game.
LIMBO - puzzle platformer
ps on pc twin stick means move with keyboard aim with mouse