Yeah, revenge has played a part in alot of Tarantino's movies but it's not usually the main plot. The last segments of Death Proof and Django Unchained are about the characters getting revenge on the bad guy/guys for what they have done to them earlier in the movie but it's not what drives them for the rest of the movie. In Inglourious Basterds, Shosanna has a plan to avenge her family's murder but that plot is augmented with the men on a mission story of the title characters. In my opinion, Tarantino's only revenge movie(s) is Kill Bill(s).
This question as to what a 'main' plot is is often confused--and can be, to non-writers, confusing. If the primary motivation of the main character--or a primary character--is revenge, and this motivation drives the narrative, then, by definition, it can (and probably should) be called a 'revenge story/movie'. (Although that is a pretty loose term.) Django's narrative is driven completely by revenge; nothing else sets the story into motion. (And, in my opinion, that is basically as far as it ever goes. It is what made the movie feel pretty thin to me, narratively speaking. It seemed to be 'about' little else, in regards to characters' motivation, and even this revenge plot isn't very well supported in the movie. We're told more about the transgressions that he wants to avenge than is shown or supported.)
I am consistently amused and intrigued by the defensive often nearly apologetic and myopic defence of Tarantino's work, particularly by young filmmakers/students. (I teach screenwriting at a major university.) For some reason--maybe his own grandstanding has something to do with it--it seems compulsory to review Tarantino and his work in the realm of the extraordinary--which I find odd in light of his actual output. I find that I like his work much more when removing the 'genius' lens and when judging the work on its own merits, for what it actually is: skilled, yet very derivative 'B' movie entertainment.
Not knocking his work, really--I love 'B' movies--Pulp Fiction is fantastic (and even features an old friend and writing partner of mine back when I lived and worked in Hollywood in a pretty great role) and I love Reservoir Dogs. Both are examples of someone with a fresh voice, who knows how to drive and pace an engaging narrative, etc. But I'm not sure I'm going to use these or any of Tarantino's work to be compared with likes of Ford's work as his trashing of him seems to want to force.