Here are the top 10 Episodes of Columbo, with the top three in boldface:

Season 2

S02, E06 — 11 Feb. 1973 A Stitch in Crime • 8.0 (2,095) +++ Nimoy

Season 3

S03, E02 — 7 Oct. 1973 Any Old Port in a Storm • 8.3 (2,361) +++ Donald Pleasance

S03, E07 — 3 Mar. 1974 Swan Song • 8.1 (2,135) +++ Johnny Cash

S03, E08 — 5 May 1974 A Friend in Deed • 8.2 (1,823)

Season 4

S04, E02 — 15 Oct. 1974 Negative Reaction • 8.0 (1,859)

Season 5

S05, E01 — Forgotten Lady • 8.0 (1,868)

S05, E05 — 29 Feb. 1976 Now You See Him • 8.1 (1,882)

Season 6

S07, E01 — 21 Nov. 1977 Try and Catch Me • 8.3 (1,973)

S07, E04 — 5 Apr. 1978 How to Dial a Murder • 7.9 (1,660)

Season 12

S12, E01 — 31 Oct. 1993 It's All in the Game • 7.9 (1,464)