You truly have to play the game without any bias to be able to rate, and actually appreciate it.
Try both LIVE 09 & 2K9, see which one you like more, I prefer Live because I don't want to spend hours just to learn the controls. So if thinking of which game to buy, play the demos first. Then decide if you like complex crossover controls with buttons (NBA 2K9) or if like to just execute crossovers with the flick of a stick (NBA LIVE 09). Don't be to fooled by the demos as well because they are no deep enough to make the decision as a whole. If possible try renting the games, what is $5 each games, when you're going to buy one of them for around $50 anyways. You will be glad you did. And remember Have FUN, because in the end that is what it is all about.