We will probably get a fire emblem game on wii u too.

Yes, these are entirely self-contained games... and each one is different in character/story and even gameplay challenges. There are some exceptions where a story can "continue" between games, but even then each game stands alone. Think of it like the Zelda series... you don't need to play all of them to appreciate any particular one fully.

The Path of Radiance and Radiant Dawn are two where I recommend play the Gamecube game first and then the Wii version because they are story-linked. Also the Wii version is hardest one to date still I think and you really should play the Gamecube one to level up your play skills.

...

Fire Emblem Awakening on  3DS is perfect one to be your first regardless.

It is one of the hardest ones but Awakening's Lunatic+ and Shadow Dragon's Reverse Lunatic are harder than Radiant Dawn's Hard mode.

It always has been for me *-*

A is Mario and Pokemon

B is Zelda, Smash Bros. and Metroid (Xenoblade may now go here too)

C is Kirby, Fire Emblem, Donkey Kong and Animal Crossing

D is better selling remainder

E/F is whatever is left

but this list is relatively subjective

It could at least reach the tier of Pikmin and Metroid.

Yes, I believe so. It was a long time coming too. I'm so proud for Fire Emblem, it may actually become a big Nintendo franchise because not only are the good games but they release on a somewhat consistent basis so, the new fans will never have to wait too long (and rage) for a new game.

Watch out Pokemon and Zelda, FE is coming to sntach your wig. 

yes i . think it will get better, i made some cousin buy it, just by showing them the game and marth :), they play on normal but i mean more sales for fire emblem !

Is it based on sales or quality?

Compared to most Nintendo franchises, no. But compared to franchises outside of Nintendo, possibly.