My subjective opinion is that a game doesn't have to be deep to have longevity. It just has to have rules that give the player different ways of approaching the rules.

For example, games like TAF and TZ might have a lot to do, but really, it boils down to "hit the ramp, then the scoop, play the mode, and move on." I tend to get tired of those types of games rather quickly. Especially when the "things to do" are linear, and also when there really aren't other ways to maximize your scoring potential.

However, games like BSD, White Water, and Doctor Who have different ways to approach the same game, and in the case of White Water, the shots are randomized in such a way that each game is different. Games need to have strategy, and different ways to approach the same objective to keep themselves interesting.