What? How's HF illegitimate? Because of the two lesser grails? Sure...Zouken did it that way. It really deviates from the others, but that's why it's interesting. You know that all 3 stories are actually 3 different worlds right? The happenings are similar, but many things occured differently. And if anything Fate/zero confirms the validity of HF.
Even if HF full of extreme things they're at least explained or plausible. While in UBW it's full of occurences somehow impossible with the previously set down 'rules'.
like:
And even if yes, hardly can the other routes compare to the emotional content of the last route.
P.S.: Congratulations for your first post on another thread! As an extra I heard there's a wild guess the Illya route actually the route EMIYA took.