Well but that is just it, FFX got me hooked on the first 5 minutes, with that blitzbal game, heavy metal song, a huge fiend attacking. And it only got better from then on, with Tidus sent "1,000 years on the future" and the weird world / society he found himself on.
Really, the beginning of FFX sucked the most, IMO. Everyone is hooked on their first Final Fantasy, because they never know what Final Fantasy is.

XII drags on and I have yet to find one memorable song. Even the opening song is fluff, more annoying than good.
The opening song was taken from FFI, FFIV, FFVII and FFVIII. It's one of Final Fantasy tradition. I dunno why you hate the opening song, though, I like it so much that I listen to it everytime I play FFXII.

The initial missions are pretty dumb too, capture a rogue tomato and a cactus with a flower on his head ? Walk around telling everyone you are someone else ? Compare this with saving a summoner on X or winning a championship of a sport as cool as blitzball. There is just absolutely no comparison!
That tomato is a monster, you face a stupid leech-like thingy in the beginning of FFX. That is far worse than the tomato. That tomato is a hunt, which introduces you to a sidequest, the main point of this game is to save a kingdom. Saving a kingdom > Saving a summoner. Blitzball sucked, just like eestlinc said, that rubbish mini-game in FFI is better. And Blitzball is another important sidequest in the game, don't compare it to "I'm Captain Basch" mini-game. Compare it to the Mob Hunt.