I don't think Generation 5 lacked Water types as much you think. There were still a bunch that you could choose from for your team. In generation 4 on the the other hand, you pretty much had to pick Chimchar as your starter because it and its evolutions were the only gettable, non-legendary fire-types introduced in Generation 4.
We need more Fire, Ice, Dragon, and Ghost types. Although, I sort of like that those last two are so rare. It sort of reflects their status as being valued/revered/feared. I guess you could say the same thing for fire types as their rarity is supposed to reflect the actual rarity of fire in nature.
An ice type that isn't so weak defensively. This is why I'm advocating an Ice/Fighting type.