Hi Ć°Åøā¢ā¹Ć¢ā¢āĆÆĀøĀ
You've got a few things back to front, and if you'll excuse me expressing the viewpoint, a misperception.
Strings are numbered higher to the lower octave. i.e. 1 to 6 is EBGDAE not EADGBE. A bit of trivia, the E strings are two octaves apart.
So you probably meant to say middle finger 2nd fret 5th string, ring finger 3rd fret 6th string, pinky to 3rd fret 1st string which describes the 'pinky G' fingering of open Gmaj? Copy that your pinky's not co-operating and falling on the 3rd fret 2nd or 3rd string.
There is no definitive "best" singular fingering of Gmaj. As you progress, you'll want both of those open forms to adapt to individual song chord progressions, and later even find youself using the barre form interchangeably. The conventional 1,2,3 fingering is the easiest to start with IMV&E. Start easy, reinforce success, progess to harder.
If instead you choose to use 2,3,4, remember the importance in fingering it of root note first, which implies landing all together if you can, but if not, ring first pinky last in that fingering where both low and high E strings are fretted, or as you downstrum in any song with a quick tempo and/or tricky chord change, the first note will likely end up being a base of E not G. Lisa covers the importance of root note first chord forming in F1.
IME&O the overwhelming majority of us won't be able to instinctively exercise the same power or consistent accuracy over our pinky (4) for some time as we do over fingers 1, 2 & 3, though even they can seem uncooperative at the very beginning. Misbehaving pinky? Time, persistance, repetition. Yep that's the 'magic' formula to bring increased flexibility, coordination and strength to the pinky.
Have fun with it. GL. Ć°ÅøĖŽ
P.S. Edit in italics for clarification.