0079 Movie trilogy - The best Gundam, bar none. Has every single core thing about why Gundam OWNS in it. Fantastic story, great motivations, , the only bad thing about this is the newtype shit at the end of the story.
Zeta - First half is AWFUL. Horrible, unlikable one-dimensional characters, poor motivations (one example off the top of my head: Oh hey, Quattro won't fuck me? Guess I better defect!

), cartoony villains (I don't like the other side to be "villains" in Gundam really, and if that, I don't like them to be so hilariously evil), poor plot. The shining light of this series are mecha/character designs which are fantastic and the last 10-15 episodes, which are excellent.
ZZ - First half is AWFUL, second half is amazing. Prefer it to Zeta.
CCA - Shit. Horrible annoying child characters, shit story, ruined Char (the best character in all of Gundam) forever.
F91 - I've...never actually seen this.

0080 - Fantastic characters, realistic motivations, it's nice to see the war on the civilian side of things, and what's more there are no newtypes in this, which makes the story even better. The best overall story in the Gundam franchise but not my favorite. Ending is amazing. One of my favorites in the franchise, probably number 2.
0083 - Great characters and character interaction, great character motivations, amazing mecha design. One of my favorites.
08th MS Team - Fantastic characters and character interaction, great story, Gundam in the jungle is awesome and refreshing. Another one of my favorites.
Victory - Better than Zeta and ZZ, that's all I can say.
G Gundam - Fucking awesome characters, great motivations, hilarious story, TEQUILA GUNDAM, really creative setting and mecha designs, hilarious battles. One of my favorites!
Wing - Solid characters (Zechs is the best Char who's not Char in the franchise, making him my second favorite character in the franchise

), best character designs in the franchise, poor character motivation, poor plot, AWESOME mech design. Cheesy, but I still really like it but that's probably nostalgia.
Endless Waltz - Shit, shit, shit. I hate this movie. Awesome mech designs, though.
Turn A - The most refreshing Gundam tv series with arguably the best worldview in the franchise. Fantastic characters, great war, great character motivations, mecha designs are refreshing (it's interesting to see a bunch of fighter planes try to take on mechs). Also has one of the best Char's. My favorite Gundam tv series.
Gundam X - This show OWNS, great characters, great worldview, great story and plot. Not as refreshing as Turn A, but it's still a step up.
Seed - I really like this show. Despite the fact that it contains the most overpowered Gundams and characters in the franchise, it has a really nice set up. The whole childhood friends at war angle is played extremely well, and casualty after casualty and the build up form one of the better Gundam tv series despite its flaws. I'd rather watch this than Zeta any day of the week.
Seed Destiny - somebody kill me
00 - first season is a shoe-in for being almost the best overall Gundam tv series. Season 2 is a shoe-in as being among the worst Gundam tv series. I like to imagine part 2 doesn't exist.
00 movie - Never seen.
Unicorn - story is LOL but I really like the characters, okay mech designs though.