In Back to the Future II, young Jennifer from 1985 sees Marty McFly and his family in 2015, observing that Marty and Jennifer are married & their son is a slacker, watching various future technology at work, and finally seeing Marty cooperate with Needles in some shady scheme (because he can't stand being called "chicken"), after which he is promptly fired by his boss. All of this seems to depict a Marty who gained nothing from his various time travel adventures, which raises the question:
- What did that Marty, age 47 or so, remember in 2015 about his time travelling adventures?
- Do those memories end at the point in Back to the Future I where Marty has returned to 1985 (i.e. without Doc Brown's sudden appearance & summons to head into the future)?
- Does he remember any/some/all/none of his journey to 2015 as a 17-year-old?
- Does he remember not just that trip but also the trip to the Old West of Back to the Future III (which presumably changes the future from what Jennifer is observing)?
- Does he remember avoiding the car crash at the end of Back to the Future III? (If so, why does Needles' taunt of "chicken?" affect him?)
His parents seem to have benefitted from the results of his first trip to 1958 (i.e. confident & happy, as shown at the end of Back to the Future I -- just older), and the older Biff character as seen in 2015 also seems to reflect the changes from those adventures as well (his outlook seems more that of a retired auto detailer, rather than having retired as George McFly's supervisor).
So some 2015 characters in Back to the Future II show the effects of Marty's first changes to the space-time continuum, but the Marty-of-2015 shows none of the resourcefulness and bravery of the 17-year-old hero. Granted, this is after his crash with the Rolls Royce and subsequent disappointments, so maybe that explains why he is the way he is.
Nevertheless, I'm curious: how much does that Marty (age 47, in 2015) remember of his adventures in a hot-wired DeLorean sailing through space & time at 88 mph?