My favorite is the 3DS Era. I was a young adult then, and sure I could say I loved 16 bit, 64 bit eras because I was younger and had much more time to play video games. But I had so much fun with my 3DS.
Specifically - 3-D integration into certain video games introduced a new way to play them, and I enjoyed the new layer in puzzles for games like Mario 3D Land and especially A Link Between Worlds.
But what I miss the most about 3DS was StreetPass. How fun it was taking my 3DS everywhere and getting visitors in both my games plus in StreetPass Plaza! I loved the hell out of those mini games and would drive all over the place to different hotspots and collect visitors! Carrying it work and making friends over StreetPass was also such a nice bonus.
Gaming was so much fun in this era and on this console. Probably still my favorite console due to all these memories tied up with it. I could get in so many gaming sessions, and if I needed to handle something quickly I could just fold it shut and go about my day. The OG suspend lol.
P.S - Street Pass is of course officially dead along with many other features of the 3DS era. However, there are archival projects so you can at least get visitors to your console. It requires custom firmware, but look into StreetPass 2 for more details.