I know it will be lame if I say it...but I have to admit I was pretty hook by EA's Lemonade Tycoon. It was pretty fun and challenging...once you get the hang of it it gets kind of old...but I really felt like a big time business man.. but instead of working on wall street I worked on the streets of the suburb.
for me it's been: -harbor master -slotz racer -pathpix -the deep pinball -galcon -frenzic -flight control -moxie -aaand space ninja
The ONLY game I keep coming back to constantly is Drop7 I keep coming back to Match 3D Flick Puzzle and Minigore, but I don't count those because they barely came out.
paper toss: wt. Although it might not be an everlasting addiction because after you play a level and get 148 in a row and then miss when your record is 150 you will most likely chuck your iPhone at the nearest wall.
My sig! Having more than 35gb of games alone, those are still getting the most playtime for me and has never gotten old.
For me, Doodle Jump or iDracula. Cliche answer but I've probably put more time into Doodle Jump than any other app I own. iDracula would be second.
Eliminate - I know everyone hates this one cause of the the pay model but I like that you can go online with the 3g. Labyrinth 2 Doodle Jump - This one never gets old.
For me probably The Creeps, Eliss (still haven't completed it) and Real Racing. There are lots of others. Thankfully saving for an ipad means I am finally getting around to actually playing some of the 350 or so games I've bought up in the past year. Buying good quality apps is like a hobby, make that a compulsion. Giana Sisters is also very very good, I'd recommend it to anyone without reservation; don't be put off by the name. Finally GT Racing keeps going up in my estimation the more I play it. I've got approx 20 hrs on the clock, I think I can safely put this on my list.