Is there some suspension of belief with regards to Batman seemingly to appear and disappear out of nowhere? Of course, but it is a lot more plausible within the context of the film for two reasons. First, we are shown that Bruce Wayne was trained in the art of theatricality and deception by the League of Shadows, including the art of stealth, so we have an explanation as to why, despite being a normal person without superpowers, he appears to have this supernatural ability to appear and disappear quickly. And second, notice that anytime Batman in those films seems to pop up out of nowhere, it's always happens in mostly open space where there is plenty room for a person to maneuver around with lots of escape opportunities.
In the case of Spider-Man and the carjacker scene, yes he has superhuman speed, but he is also in an enclosed and compact space, specifically the backseat of car which the car thief has to break into since it has locked doors and rolled up windows and not a whole lot of room to maneuver around in. Now is it possible that when the car thief used his electronic unlocking device that it unlocked all the doors at once allowing for Spidey to quickly get in? Maybe. And is it also possible that Spidey quickly opened the back door and left just as the quickly as he got in (some have heard there was was what sounded like the closing of a door just as the car jacker got out). Unfortunately, the scene either doesn't make this clear enough or doesn't really allow much room for either of those possibilities, IMO.
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