Top 10 Free-to-play MMORPGs with a speedy level-up system

The MMO world is fairly similar to its predecessor offline RPGs, it's all about character growth. Some gamers, regardless of what MMO it is, would want to level up their characters so fast to explore more of the game or feel a sense of achievement. Generally, it's safe to say that all MMORPGs have this certain speed in terms of leveling. However, some games have leveling systems that grow characters faster than the others...