I remember using the red Gyarados on my first playthrough of Gold, and being really excited by her. She became a permanent teammate that went down in the Hall of Fame at the Pokemon league with me.
I also used the red Gyarados as a full-time player when I revisited Johto in HGSS and remember even saving space on my team in anticipation of this pokemon's arrival, deliberately not training up any other major water pokemon. He was with me till the end battling Red by my side.
In Gold my starter was Typhlosion and in Soul Silver it was Meganium, so Gyarados was easier to fit on the team, but when I played Crystal I remember choosing Feraligatr, and as a result Gyarados didn't see as long of a tenure, but I did still use it in battles sometimes, and made a point of battling Team Rocket with it in Mahogany Town. It deserved at least the chance to take revenge for how they destroyed it's habitat.
Gyarados is a pokemon I like in general, all things reminiscent of dragons appeal to me, and having played with it in many games in various generations, I just see it as a reliable attacker and I like to go to it when in doubt, and if I have the option of a magnificent-looking red shiny variant that is not something I will put aside lightly. No sir.