That's a very symbolic sequence. Up until that, you have totally faceless interchangeable stormtroopers. But the blood mark on his helmet make him an individual; all other stormtroopers are totally anonymous but he is now recognizable. And as an individual, he can make choices (and of course, he chooses goodness and freedom).
It is as good as the original. It's only problem is that the original exists, and so it suffers by comparison; on its own it's almost worth every bit of praise that comes (weakest bits being the treatment of Kylo Ren and Phasma's non-presence).
Try (as hard as it might be) to think how you'd see it if there had never been an original trilogy. If it was the first movie of a new franchise. There's a couple bits that don't work well (the obsession with Vader, R2D2 & C3PO don't make sense at all outside of their original presence, some snark remarks; and of course why that old guy on some desert island would be important to everyone), but the rest would absolutely make a kickass movie.
Of course, it would never be the first movie of a brand new, never seen franchise; Hollywood doesn't take that level of risk anymore.
I think most of everyone pieced it together; Rey is the only survivor of the slaughter of that new Jedi Academy Luke had founded by the Knights of Ren. Ben Solo prevents her kill for reasons (she's his sister? cousin? he liked her due to random? she's the only girl there and he's still not evil enough to kill little girls?) and drops her on Jakku when she's like 5 year old. She's repressed those trauma memories and built instead that fantasy that her family is going to come someday to take her away (why have "jedi mindwipes" when nature does it almost as good as any force trick). No one would recognise her fully grown up, and even Kylo Ren is not sure if that's her at first, at least not until she mindgrab the lightsaber. Of course, Luke will recognize her because Force stuff (or being his daughter, if she is), but I doubt anyone else except Kylo Ren knows the truth at that point.
The Force Awakens is of course Rey's coming back into the Force, no discussion about that. I've seen some people think it refers to Luke leaving his exile, but that's incorrect.
