Name 'em!
List 'em!
As long as you put down the name of any legendary of any generation.

My personal favorites would be...
Mewtwo (enough said)
Mew (no explaining needed)
Articuno (looks cool)
Ho-Oh (again, looks cool)
Kyorge (no real reason)
Jirachi (is strong in battle)
Giratina (epic battle music in platinum and looks cool)
Arceus (because)

My top five are Arceus, Mew, Mewtwo, Giratina, and Dialga. Arceus for its design, status of God of the Pokéverse, and backstory, Mew for being awesome, Mewtwo for also being awesome, Giratina for its design and role in the games, and Dialga for its design, backstory, and role in the games.

I guess I'll say shaymin because it's delicouse.

Giratina, Arceus, Dialga, Mew, and Raikou. Giratina for it's sheer epicness, Arceus for.... idk, Dialga for blueness, Mew for teh best legend, and Raikou because he looks cool.

Mew. It's a freaking cat. With the ability to do ANYTHING.

Mew, Ho-oh, Dialga and Giratina are my main favorites.

Deoxys. Despite being a cheap, overpowered, unobtainable uber, it's FRICKEN AWESOME. Also Lugia, for the nostalgia, and Cresselia, because I like it.

1- Dialga
2- Deoxys
3- Grouden
4- Mewtwo
5- Lugia

(Not in any particular order)

Zapdos
Suicune
Lugia
Latios/Latias
Rayquaza*
Deoxys
Giratina**
Arceus

___________________
*I chose Rayquaza over Groudon and Kyogre (which I also like), as it is the most awesome out of the three.

**I also like Dialga and Palkia, but again, Giratina remains my personal favourite over the other two.

My favorite is Rayquaza

Lugia, Mewtwo, Dialga, Arceus, Giratina, Groudon, Deoxys, Latios, Darkrai, Raikou.
Long list, thus I can't be bothered to list every reason for each legendary.

Rayquaza is my absolute favorite. Lugia is my second fav.

(in no particular order)
Azelf, Palkia, Jirachi, Celebi, Shaymin, Arceus, Kyogre, Moltres, Ho-oh, Mew

Groudon
Rayquaza
Kyogre
Lugia
Dialga

Regigigas, something about the general design, combined with the slow start and high stats after waking up makes him seem artful to me.

Mewtwo.

1- Mew
2- Raikou
3- Rayquaza
4- Ho-oh
5- Deoxys

Mew & Jirachi. I dunno why.

My favorite overall would have to be Articuno - such an elegant bird that's so... freezey .

Mew, Lugia, and Rayquaza are also up there.

Cresselia! I always found her elegant, and the high defenses she has makes her hard to take down.

My favorite is Mew because its so cute and it can learn any move and Articuno because it so pretty.

Moltres. The legendary birds are my favorite legendaries, and fire is my favorite type.

My favorites would be Arceus, Dialga, Rayquaza, Celebi, and Mew.
(is Lucario a legendary? I don't consider him one, but I'm not really sure.)

I like Mew and Arceus. Mew, since it can learn ANYTHING and Arceus, its type changing and awesome move, judgment!

Rayquaza and Zapdos owns.

Lugia and Ho-Oh are pretty birdies, Giratina is awesome, and Mew's a kitteh. :3

Mewtwo, Jirachi, Groudon, and Dialga.

~Chris