https://boardgamegeek.com/thread/1116308/top-150-best-gateway-games-results
Top 150 Gateway Games
1 Ticket to Ride/TTR Europe
2 Carcassonne (all)
3 King of Tokyo
4 Dixit
5 For Sale
6 Diamant/Incan Gold
7 Can't Stop
8 Pandemic
9 Love Letter
10 Settlers of Catan
11 Takenoko
12 The Resistance (& Avalon)
13 Forbidden Island
14 Survive!
15 Alhambra
16 No Thanks!
17 Hanabi
18 Dominion
19 Stone Age
20 Crokinole
...
I like pretty much all of these (except for the cooperatives like Pandemic) but I see them as appetizers, not the main event.