My opinion about best possible first move by white can be summarized this way:
1.) Apart from e4 and d4 all other moves are inferior. There is nothing that you can achieve with other moves that can not be achieved by e4 or d4, but you risk certain disadvantages by moves other than d4 or e4.
2.) Though e4 looks more sharp and dangerous in reality black has ample resources to equalize. Very dangerous looking and agressive lines in e4 openings like the Kings Gambit or Scotch Game are in reality more dangerous to white than black. Even the Ruy-Lopez, which is truly a solid line can be equalized by the Berlin defense in a foolproof way.
3.) Objectively speaking the positional 1. d4 is the most powerful move that white can make because it guarantees lasting spatial advantage which black will find hard to break. The best for black is to accept the spatial disadvantage with some Queens Gambit Declined formation because the alternative is to engage in potentially suicidal hypermodern maneuvres. All in all white has more lasting chances to break black's resistance and at least a comfortable draw is not in jeopardy with this system. While in the sharp e4 system things can very quickly and very easily turn against white.
1)1.Nf3 and 1.c4 provide transpositional opportunities to white and allow him to control the opening moreso than if he(or she) plays e4 or d4. Nf3 and c4 are NOT objectively inferior
2)2700+ players might whole-heartedly disagree with you here....if equality was foolproof against the Ruy than 1.e4 would cease to be played.
The only alternative to the QGD is Hypermodern stuff? What about the Slav, QGA, Nimzo, etc.? And dismissing KID, Grunfeld, etc. as "potentially suicidal" is also sorta ridiculous, especially given the topical-ness of the Grunfeld at Super-GM level lately. And I wouldn't necessarily say the KG or Scotch are "more dangerous for White". Or that the Berlin is "foolproof". etc, etc. etc.