I haven't played + or e+, but I doubt many people play those games anyway, I've played the rest though, so here's my personal opinion.
1. CF/LGTTC
2. WW
3. GCN
4. N64
5. NL
I don't play GCN and N64 that much, and N64 is basically GCN with less features and minor differences. They are both fun to play, especially GCN since it has more content. Plus and GCN fixed a lot of the problems N64 had, apparently, which is why I ranked GCN higher. I've heard e+ is like the jump between GCN and WW, someday I might get it.
WW is what I consider the better of the two handheld games. It removed and butchered a lot of the stuff GCN had, but it also had plenty of new features, and I really like the touch controls. This one has my favorite villager dialogue, and the special NPCs had more fleshed out personalities. There's a large amount of new characters, along with new villagers, such as the monkeys, Ruby, and Whitney. It had amazing graphics for an early DS game, and has good graphics for the DS in general. It introduced my favorite Animal Crossing music. Many more new things were introduced as well, such as tools. Villagers wouldn't simply move out without notice and would be in boxes if you visited their house when they were trying to move. For the first time, you could play AC with friends near and far. This game made AC like it is today. However, it loses points for the removal of most holidays, one of the biggest aspects of GCN, and overall having the removal of many things from GCN. It was still very fun, however, and is my second favorite, only behind CF.
CF was a game that improved on WW. It introduced new NPCs, villagers, and various features like it's DS equivalent. One of the biggest things it improved on was the online. You could now do things such as have K.K. play a song while friends were over. With Wii speak you could chat with friends faster, and with your own voice. There were default messages you could click on so you could chat with someone in a simpler way. It also had a city where most of the shops were all in one spot so you didn't have to run back and forth between one spot in your town and another. Silver tools were introduced, which weren't as weak as regular tools, but weren't the ultimate gold tools. The graphics were the best yet. Some features from GCN returned, such as holidays, ledges, Wisp, and various villagers cut in WW, while still retaining most of the features from the previous game. You could degrade your Nook store if you wanted to after you unlocked Nookingtons. However, it loses points for having not as decent villager discussion as WW, the grass destruction, and not being able to go to the city with friends. It is my favorite AC game.
NL appears to have thrown almost everything CF introduced out the window. Even store degrading, which would have fit perfectly with being the mayor, was cut. The mayor feature didn't even have much. It was simply a few minor gameplay changes, and PWPs, which already existed in e+. Dream towns felt pointless to me, as you couldn't take anything from there back with you. Red turnips were removed and not replaced with anything. The artstyle changed completely, and now it's much too realistic. It appears to have lost that Animal Crossing charm. (Also, Tom Nook is now wearing a sweater which I find to be ugly, no offense.) I didn't really like the music, to be honest. The town layout seems to be the most boring in this game, with no ledges or special features like islands, bays, or canyons. The only features which I think stand out are club tortimer, and best friends chat, and both will become useless when the online is cut off. If anything, it's a spiritual sequel to GCN, which is what CF pretty much is as well.
I've also played HHD, but I can't really rate it since it's a spin-off. I like Lottie though, I hope she has a major role in the next new AC game.
These are just my opinions, you don't have to agree with them.