Risk is the most-recognised conquest game in the world, and one of the most-criticised on r/boardgames. The fundamental tension is that Risk has real strategic depth — Australia first, control bonus continents, manage your reinforcement rate — but the experience is undermined by extreme game length and player elimination.
A standard six-player Risk runs four hours and eliminates two or three players before the end. Once you're out, you sit and wait. This is the single most-cited reason groups switch to Risk: Legacy, Twilight Imperium, or modern alternatives like Scythe.
The community-recommended fix is the "blitz" rule (attacker keeps rolling automatically until they win or have one army left) which speeds up the dice gauntlet. With blitz + a 3-hour timer, Risk becomes a Saturday-night game again.
Risk: Legacy (2011) and Risk 2210 A.D. are universally considered improvements on the base game. Legacy in particular — a 15-session campaign that permanently changes the board and rules — is one of the highest-rated games on BoardGameGeek and worth owning even by people who hate the original.