I will certainly rate Golden Mahseer as the best fresh water game fish because :-
1. Due to its fighting characters.
2. Due to the size this fish can grow.
3. The terrain where you target this fish in itself a joy to walk.
4. You can target this fish with all fishing techniques. Bait Fishing, Spinning, Trawling and Fly fishing can all be used to target this fish. Whatever is your preferred technique, you can use against this fish.
5. In a misty morning, when the sun is rising over the horizon, and the colour of the water is like molten gold, you see this fish rising over the water and that alone is an experience one can cherish for life long, not to mention the flicker of gold chasing your spoon, the express hit, fish standing vertically half out of water, shaking its head to dislodge the un wanted spoon, the maddening rush and your reel singing---- It can only be understood by experiencing one good fight.
There are thousand more reasons but I think the above is more than sufficient to make this fish no. ONE.