(WITH 50% PROBABILITY THIS WILL ACTUALLY START AT 2:30; I WILL UPDATE THIS A LITTLE AHEAD OF TIME)
99 is, in my opinion, the best trick-taking card game, and one of the only competitive games for more than 2 players that is not degenerate. These opinions are corroborated by ~everyone I've taught to play this game, with any prior interest in imperfect-information turn based strategy games.
For reference, games in the same genre that I think this dominates include hearts, spades, shengji/zhaopengyou, and skat.
Some ways in which this game is awesome include:
High proportion of active play time (due to the bid structure, most hands are playable for all players, unlike with poker or some cards)
Rapid iteration (rounds last 5-15 minutes, and not much longer even just after reading the rules)
A strategically rich bidding phase and play phase -- the graph of interdependencies between hidden variables in the game is highly connected; every action taken sheds a tiny amount of light on every hidden variable.
Various distinct mechanisms for skill-based play (there are several competing objectives; it is possible to shoot for points by more than one mechanism, and it is feasible to actively sabotage opponents by misleading them or inferring their objectives)
Low memorization burden (there are only 36 cards played out over 9 tricks; since there are only 9 cards per suit, 3 players, and people run out fast, there are a lot of semantics to hook on it becomes achievable to memorize all played cards with relatively little experience and no deliberate effort)
Given the above, if you were interested in playing MegaGem, there's a very high chance that you would enjoy playing this game.
The rules can be found here: https://www.parlettgames.uk/oricards/ninety9.html