Hmm... FFX. Despite the fact that I fell asleep the first time I played it, it is one of my favorite FF games. Can I be analytical towards it for a minute (and by minute I probably mean more like 5 or 10)?
One of the great benefits of FFX was that until the last part of the game, every single character had a unique role in combat and switching them in and out as necessary was easy. All of those things could have happened in real time, just not as easily or as effectively (okay, to be honest, it would have been craptacular). Tidus was the man if you needed speed, Wakka if you wanted someone who could hit some of those dodgy baddies, Lulu for physical resistant baddies, Auron against heavy defenses, Yuna for healing (and for the best Summon system I've ever seen in a game to date), Rikku as a sort of situational specialist (her role, unfortunately, felt the weakest to me), and Kimari to play as support for whatever area the individual player felt was needed. Beautiful; the game is worthwhile to play for the system alone.
Lord of the Rings: The Third Age tried to imitate the system, unfortunately it did so rather imperfectly, a result of the skill system used in that game, actually (if I am remembering right, one has to use a skill type to gain new abilities in that skill group). This resulted in players really needing to focus on a few characters, and a few skill types, to really level those skills up and get amazing attacks. I think this reveals the flaw with The Third Age and the beauty of FFX: their skills systems in comparison to their combat method (that is, in comparison to being Turn Based RPGs).
In FFX, the Sphere Grid works wonderfully; sure, it limits a character's advancement to one or two very specific lines of progression until late in the game (when the sphere grid can be largely unlocked and characters warped around it, so that Auron becomes as fast as Tidus, as accurate as Waka, and as supportive as Yuna), but for the majority of the game the grid's restriction forces characters to stay in unique roles; there is little fear that Tidus can replace Auron early on, which forces players to use all characters fairly regularly. Add to that the fact that the sphere grid offers a lot of advancement, players get rewarded after almost every battle (small rewards, usually, but the sphere grid spaces larger rewards well enough that a player gets a larger reward fairly often). If we took these non-turn-based elements away from FFX, I think it would be much less interesting to play and I doubt many of us would be holding it up as a wonderful example of the style.
The Third Age, on the other hand, had levels that resulted in stat points to allocate and skills that developed by use. At level up, players could make all the characters equally as physically powerful, accurate, or whatever. But because of the characters skills and basic nature leaning towards a particular direction and role, the freedom to develop character stats as desired was largely illusionary. In the end, it was slightly more flexible than the Sphere Grid, but by removing skills from the equation (that larger rewards mentiond above), it made leveling less interesting and reduced each character's uniqueness in combat (thereby reducing the amount of time one character would be switched out for another, which in turn reduces the dynamic nature that the turn based combat was complementing, and at the end making that turn based combat less fun than it could have been). Because skill types could only improve with use, it forces players to fall into ruts. Characters are then chosen for combat not based on their actual immediate use but on their long term development. Though there was greater complexity and more player choice opportunities than the Sphere Grid presented, it ultimately actually led to less variety and complexity in combat (and if there is less variety and complexity, one can more easily get away with Real Time combat as opposed to Turn Based).
Thus, for FFX, turn based combat complemented (and was complemented by) a beautiful character progression system. If there hadn't been that synthesis, then the result would have been much less spectacular.