Here are some marathon win streaks, by some of the most dominant men of different eras, 1950s to present. There are of course big differences across these eras, but in each of these cases, these men were among the most dominant for a time. I am including some that have DNFs in them -- I don't care either way, but they are included here for consideration, and partly to emphasize how incredible Kipchoge's current streak of 7 or 8 (depending on your attitude toward the Monza race) actually is. With or without Monza, it is a great streak, winning in fast times against most of the best competition of this era, no DNFs. Kipchoge's streak, among top-level marathoners, is unequaled.
Jim Peters 7 (from his marathon debut in 1951, ending with his 2nd at Boston 1954. This streak includes DNF at the 52 OG. Longest DNF-free streak here is 4.)
Abebe Bikila 6 (from his marathon debut in 1960, ending with his 5th at Boston 1963; he also had a streak of 5, after that loss, to the end of his career, with 2 DNFs.)
Derek Clayton 5 (from his marathon debut in 1965, ending with his 7th at Mexico City OG)
Frank Shorter 8 (from his Pan-Am win in 1971, ending with his 4th at Honolulu 1974. This includes a DNF in 1973, and an =1st at the 72 USOT. Longest DNF-free streak here is 6.)
Bill Rodgers 10 (from his NYC win in 1976, ending with his 6th at Fukuoka 1978. This includes a DNF at Boston 1977. Longest DNF-free streak here is 6.)
Toshihiko Seko 5 (from his Fukuoka win in 1979, ending with his 14th at 1984 OG)
Rob DeCastella 4 (from his Fukuoka win in 1981, ending with his 5th a 1984 OG)
Haile Gebrselassie 8 (from his Berlin 2006 win, ending with his 4th at Tokyo 2012. This includes 2 DNFs within the streak of 8. Longest DNF-free streak here is 5.)
Sammy Wanjiru 4 (from his 2008 OG win to his last marathon, Chicago 2010. This includes one DNF.)