Quantity does not equal quality. Just because games are long doesn't mean they're telling a good story. In fact it's usually the opposite, especially with JRPGs. They tend to start strong but have very weak (and long) second acts, while the quality of the endings are all over the place. On top of that, most of the time is spent travelling or fighting. The actual story segments could probably be compressed into a few hours at most.
Final Fantasy games are more about atmosphere than story. Their plots are not that strong when compared to any other medium or even some other games.
Tales of Vesperia, like most Tales games, is more about the characters and the themes than the plot. The characters in Tales games are usually strong and likable, the themes are clear and understandable, while the plots are a bad excuse to have everybody running from dungeon to dungeon.