I have fond memories of Phandelver because not only did my wife and sons to play it, but I got my mom & dad (who were in their 60's, and now passed away, and hadn't played since they bought me the Holmes set for Christmas in '79) to play as well - as well as my younger brother and his wife. Three generations, all in one game - and everyone enjoyed it greatly.
And there was the Castle Ravenloft one-shot I ran for my son and his friends (who he'd just introduced to D&D because of our Phandelver game) using Curse of Strahd (Start of game: "Ain't 'fraid of nothing, it's just a game.", about one hour later "I AM NOT LEAVING THIS ROOM UNTIL DAWN!!!!!").
Many other adventures over the years, including a very enjoyable one with Falkovian zombies using the much maligned Van Richten's book. I got to play with a multitude of people (many much younger than me) in these campaigns and it helped to keep me feel connected to world and not feeling quite so old and dinosaur-like.
Also, since the longest time, I've done a lot of gaming from the player side of the screen and got to play some really interesting characters, hoping that I encouraged others in delving into giving life to their own characters beyond the stats on the sheet. I think my favorite has been my boisterous centaur sage-priest (Enourmuus) in my co-worker's game of Theros. Seeing what players want out of the game has really relaxed my years of frustration as a DM to fret over keeping a game balanced (and challenging) and being more permissive about what they can accomplish.
So, beyond happy memories, what would I say are the standout products? Well, put me down for Mines of Phandelver, Curse of Strahd and Ghosts of Saltmarsh for adventures. Xanathar's Guide to Everything is, in my opinion, the best supplement and fills in a lot of needed gaps from the core rulebook. My all-time favorite monster book is Monster Manual Expanded II, though I like the entire Expanded series and Mordenkainen's Monsters of the Universe. As far as campaign settings go, put me down for Planescape and Mythic Odysseys of Theros.
As far as innovations go, I really like the Class/Subclass structure - it comes in at just the right time in character advancement as a sort of promotion from the "beginner" levels. I also greatly enjoy Ideals/Bonds/Flaws and don't want them to go away - they're such wonderful roleplaying tools (since Alignment seems to be dying on the vine). I also greatly appreciate Bounded Accuracy as the constant chase for bigger/stronger numbers I've long tired of.