Below are all top sets by year:

Top 25 sets of all time

1 -42043-1 Mercedes Benz Arocs 3245
Total: 14911 sets
Theme: Technic
2 -42009-1 Mobile Crane MK II
Total: 14325 sets
Theme: Technic
3 -42030-1 Remote-Controlled Volvo L350F Wheel Loader
Total: 13384 sets
Theme: Technic
4 -42055-1 Bucket Wheel Excavator
Total: 11429 sets
Theme: Technic
5 -42056-1 Porsche 911 GT3 RS
Total: 10960 sets
Theme: Technic
6 -10220-1 Volkswagen T1 Camper Van
Total: 10799 sets
Theme: Creator
7 -9398-1 4 x 4 Crawler
Total: 10594 sets
Theme: Technic
8 -10243-1 Parisian Restaurant
Total: 9954 sets
Theme: Modular Buildings
9 -21309-1 NASA Apollo Saturn V
Total: 9792 sets
Theme: LEGO Ideas and CUUSOO
10 -8110-1 Unimog U400
Total: 9638 sets
Theme: Technic
11 -8043-1 Motorized Excavator
Total: 9366 sets
Theme: Technic
12 -10218-1 Pet Shop
Total: 8155 sets
Theme: Modular Buildings
13 -10232-1 Palace Cinema
Total: 8119 sets
Theme: Modular Buildings
14 -8293-1 Power Functions Motor Set
Total: 8057 sets
Theme: Power Functions
15 -10246-1 Detective’s Office
Total: 7875 sets
Theme: Modular Buildings
16 -42082-1 Rough Terrain Crane
Total: 7578 sets
Theme: Technic
17 -42054-1 CLAAS XERION 5000 TRAC VC
Total: 7477 sets
Theme: Technic
18 -42065-1 RC Tracked Racer
Total: 7367 sets
Theme: Technic
19 -42039-1 24 Hours Race Car
Total: 7181 sets
Theme: Technic
20 -42078-1 Mack Anthem
Total: 7148 sets
Theme: Technic
21 -21108-1 Ghostbusters Ecto-1
Total: 7120 sets
Theme: LEGO Ideas and CUUSOO
22 -75105-1 Millennium Falcon
Total: 6971 sets
Theme: Star Wars
23 -42006-1 Excavator
Total: 6617 sets
Theme: Technic
24 -42042-1 Crawler Crane
Total: 6570 sets
Theme: Technic
25 -10251-1 Brick Bank
Total: 6354 sets
Theme: Modular Buildings