All three.
Narratively, the first half is nearly identical to the original series with less "gritty" drama. To be fair, the second half is ok at least.
Animation-wise, the artwork is very crisp, but just about everything is stock-footage.
In terms of characters, you'll end up hating 80% of the cast. Also, the main character Kira is probably the most hated ever.
I'm not as harsh as you regarding animation (I think it's generally passable), but regarding characters - seconded 
On top of this, Destiny's 100% worse... 
Seed and Destiny are usually clumped together as a single entity, they're basically a season 1 and season 2 of a single series.
It's not just the crappy characters, its the boring ass plot and the stupid ass grunt suits that basically sit there waiting for Kira to shoot (watch after war x for grunt suits that can take a direct hit by a buster rifle and still survive as well as having capable pilots). The stupid romance between Lacus and Kira is so unbelievable it makes you cringe, it feels so fake. Cagalli and Athrun was a better romance which was not exploited to its fullest. The shinn and Stellar romance just sucked ass. Compare this again to After War X, Garrod and Tiffa had a believable relationship that was developed more so than anything in Seed (including characters and plot). The fighting scenes were re-used almost every episode, just changing the gundams being used every 30 or so eps.
Seed/Destiny has absolutely no qualities that make it better than any other Gundam series, that is to say, in every single area that it can be fleshed out, all other gundam series are better.
It's only popular and well received because it came out recently. Had any other Gundam series came out in 2003/2004, it would have been better received.
Destiny is a re hash of Seed with an extra "bitch" of a character (but admittedly Kira is less annoying)