I don't think using current Amazon charts is a good indicator for Street Fighter V. A lot of people would have already preordered the game much earlier to get into the beta, which by all accounts have had a huge turnout.
And yeah GR2 isn't going to sell much of anything in retail. Sony knew that which is why they kept the physical copy Amazon exclusive (except for poor Canada).
I don't think GRR is going to sell much of anything in any form. I don't expect to undersell itself ala Tearaway... well, one would hope not as there's a sequel in the works.
As for SFV, only reason I find it notable is because its totally absent from Japan's trackers as well (and the bottom of the barrel isn't exactly... lively). But you do raise a good point on the Beta but the idea of a "huge turnout" doesn't really gel with statements like:
Decent numbers. Fighting game fans coming out of the wood work more with each beta/news update. I think it'll be the gradual burn that gives it legs.
The title in general just seems like its moseying onwards towards release, and it feels like it has no wind in its sails. It will sell to the fans but... feels like that's it.