I think most of the nostalgia for Dragonlance comes from the timing of the release of a novel line that directly related to the RPG product line. The Dragonlance series of adventures were a connected storyline that put the PCs in the position of determining the course of the War of the Lance, even if the affect on the war was already scripted by the railroad-y modules. These modules were released before the first three novels I believe, so the first players running through them didn't know what was coming next in the adventure path. Now I admit I'm not sure of that, I haven't gone back to check publication dates. But the novels were written based on the playtesting of these adventures in Weis and Hickman's homegame.
For me, Dragonlance is special because the novels were the first fantasy series I read when I was first starting to play D&D around the age of 9 or 10. So I think them being my introduction into novelized fantasy colours my opinion of them to an extent. They aren't the best the genre has to offer, but as far as epic fantasy goes, I think the first 6 novels stand up among the average, considering the massive amount of titles in the genre that have been published in recent years.
As a campaign, I compare running Dragonlance as being comparable to running a Star Wars game. If the players have read the books they can all have a common background of the basics of the setting, and can participate at the edge of major events, or make up their own epic journey throught the setting.
Selling points as I see them:
• The PCs can participate in the major conflicts throughout the different ages, either replacing the characters of the novels or in events that don't involve them, or these conflicts can act as bookends to define a common starting point similar to Ebberron's Last War. These conflicts can include The War of the Lance, The War of Souls, the two Cataclysms, etc.
• Good versus Evil world-wars.
• More Dragons. I like having dragons as main antagonists, and the fact that they ally with lesser races gives more oportunities to use them in adventures and dungeon building.
• Different Races - There's three subraces of elves (not including aquatic), many more dwarves, plus the wackier ones like Tinker Gnomes, Kender, and Minotaurs. I like a bit of humour in some parts of my rpgs so the comic relief races don't bother me.
• The first continent detailed, Ansalon, is in the southern hemisphere of the planet, so the icy cold part is at the bottom of the map rather than the top for once.
• No Orcs. Fight different humanoids at low levels for once.
• No Drow or larger Underdark societies. With no great underdark cities or cave systems the adventure design is a little different. But there's plenty of adventure locations scattered throughout the campaign guides, usually the remainders of pre-cataclysm civilization.
• It can be points of light-ish in the post-cataclysm setting as civilization is largely fragmented, and there are few empires or monarchies left. Lots of space for adventuring in between.
• Order of knights whose defining features apart from their honour code are their mustaches.
• As stated above, Draconians. The original dragon-men in D&D, and one of the great gotcha-monsters.