As a Final Fantasy game, there are things that could have been changed. Overall, it's still a great game.
The story is just what's expected of a good Final Fantasy game. There's a world-wide, cataclysmic problem, a big, scary antagonist, and a love interest between the main character and the girl that he just met. In all, the storyline is simply great. It keeps you hooked with every element you need - action, romance, suspense, and more. It will surely leave you wanting more.
Final Fantasy X has a fairly similar battle system to it's predecessors. However, rather than using a traditional turn-base (Final Fantasy I) or active time-base (Final Fantasy VII) it sports a conditional time-battle. In this type of turn-base, a character's actions are selected at the beginning of his or her turn, performed, and then comes the next character, (unlike the traditional system where everyone's actions are selected at once.) Also, any characters can be switched out for benched ones at any time during battle (providing that they're alive). This being said, the battle system of Final Fantasy X is quite a bit easier than past games. On the other hand, if carefully planned strategies are more your thing rather than quick reflexes in games, this would work for you.
If you've played past Final Fantasy games, you're probably aware of the summoning system. Before, your characters could summon large, beastly entities who would perform one powerful attack before vanishing again. However, in FFX, the Aeons (as they are called here) will take the place of the entire party and remain there for the player to control until it is either defeated or dispersed. This adds a nice touch to the game, as something new and exciting to try out during battle. Many past summons make a reappearance, and some new ones as well, but whether old or new, they are possibly the most artistically-done aspects of the game. The detail and mystic air that the designers instilled is really amazing.
Another note in the game-play, there is no more world map. Square-Enix wanted to create a larger sense of realism, since it was a huge milestone in many other aspects, so it seems that they found that largely-spaced-out towns that were smaller than the player didn't look realistic. Anyway, this game is VERY linear. There's almost no way to get lost, as each location is directly connected to the next. This did take away a lot of boring map-hiking, but it also took away a sense of freedom when the game just starts shoving you in one direction. Random encounters remain common, though, and you do still receive a chance to do the occasional sidequest.
The overall graphics are fantastic. FFX really is a milestone in the Final Fantasy series. Now, the franchise has full-sized, detailed, and completely realistic-looking characters. The cut-scenes are even better! SE also outdid itself with the scenery, and every monster and critter is brought to life.
Final Fantasy X is also the very first game to have voice-acting, which was one of the most anticipated aspects. Now, the characters seem much more life-like and human, rather than just being a group of pixels on the screen. Although there are some characters whose voices I couldn't stand, (I'm looking at you, Wakka! Ya?) SE still did a really good job.
There is also really good replay value, too. After you finish the portion of the game up to the final dungeon, there are a load of new things to do. (This is where you finally get some sought-after freedom in this game.) The biggest side quest it the monster arena, which is run by a man who essentially sends you off on something like a Pokemon hunt. No, really! You receive special weapons that will "catch" a monster when you defeat them with it. After catching certain groups/species/amounts, special bosses will be unlocked (Bred, actually. o.0) at the arena which will end up acting as a huge group of superbosses for Final Fantasy X. What fun! Seriously, it's fun to be catching all the monsters and even more fun to take on the souped-up versions of them and squishing 'em!
So, overall, this is a pretty good game. There were a couple issues, but they were pretty easy to get around. A great storyline, an alright battle system, good replay value, and fantastic effects all added up to one awesome time. I'd recommend it to new players to the genre especially, since the battling is easier and slower, but it's still a great game for absolutely anyone else to play.