Don't know why, but I don't want to miss Spa. Actual race is a bit boring though. IMO, other fun races off the top of my head are Silverstone, Baku, Austria, Bahrain, Suzuka
Of course the "usuals" of Spa, Suzuka, Silverstone. But COTA consistently provides great racing (despite some of the flaws of it). I also really enjoy watching Brazil, of course.
Spa, Silverstone and Singapore. Why Singapore? Well before I started watching F1 I was playing the F1 racing games in like 2011 and Singapore was my absolute favourite circuit to drive, I still enjoy playing it now actually.
I enjoy Red Bull Ring. Always some decent overtakes. Hamilton running Albon off the track when he was looking like getting his first podium in the Red Bull wasn't one of them though.
I appreciate that it is a bit far for many of you to travel there, but Melbourne is fabulous on so many levels - the racing, support program, access etc
Interlagos, Spa-Francorchamps and Monza are historic venues. But I am biased and think that circuit Gilles-Villeneuve is also a classic.
Crazy first corner, tight walls, wall of champions, epic races and accidents. Gotta be worth something.