In essence - lighting, composition.
None of those photo's are thoughtfully composed or lit.
It's been said a thousand times already this year here, but no amount of effort after the fact can recreate the effort required before you press the shutter.
#1 Nice contrasty light was available, if the rider was turned 30deg clockwise the sun would be lighting the face better, the composition is thoughtless, cutting across the horses legs and filling 1/3 of the frame with sky?
#2 Shot in the shade. lacks any contrast, area of interest created by composition or lighting.
#3 is the closest to a decent picture, just a slight move of the horses head would have lifted the eye out of shadow, and a connection would be made. atm the focus is on the buckle and there's no real interest.
There are definitely better angles to explore for all of them, but I'm not an expert. Have a look at
this he's a member here and should give you some inspiration.