A games night is one of the easiest events to start and one of the easiest to let quietly fade. The first one has novelty energy and everyone turns up. By the fourth, attendance is a coin flip and the group chat has gone quiet. The difference between a one off and a fixture is almost entirely in how you run it, not in the games.
Lower the barrier to the games themselves
The fastest way to kill a games night is to open with a forty minute rules explanation for a heavy strategy game while three people stare at their phones. Start with something everyone can learn in two minutes. Party games, quick card games, anything where the first round teaches the rules. Save the long games for once people are warm and committed, if at all. The point is the people, and a game that takes half an hour to set up gets in the way of that.
Have more food than games
Games nights run long, and people get hungry and tired. A few easy snacks and a steady supply of drinks does more for the night than a bigger games collection. Nobody remembers which game you played third. They remember whether they were comfortable and fed while they played it.
Make it the same night, mostly
Recurring plans stick when the rhythm is predictable. The first Thursday of the month, every other Tuesday, whatever fits the group. When people do not have to renegotiate the date each time, it slides into their routine and stops competing with every other plan. Set it up as a recurring event so the next one is already on the calendar before anyone has to remember to organise it.
Make missing one no big deal
The thing that kills recurring groups is guilt. Someone misses two in a row, feels awkward about coming back, and drifts off. Build the opposite culture. Each session stands alone, the invite goes to everyone every time regardless of who came last, and you never comment on attendance patterns. People should be able to skip three and return on the fourth as if nothing happened.
Keep the circle right sized
Games nights have a natural size, usually somewhere between four and eight depending on what you play. Too few and it is flat, too many and half the room is waiting for a turn. If your group is bigger than the games comfortably hold, run two tables rather than one big one. A right sized table has a better night, and people leave wanting the next one.