My first shooter was Call Of Duty Modern Warfare, and I loved it. I thought the story and game play were really well thought through, and it's still my favorite Call of Duty and one of my favorite shooters. Since then shooters have become one of my favorite genres of game, because I believe they are outstandingly realistic and players are fully immersed in the whole experience.
Don't regret anything, still play it to this day. Light game filled with fast paced action that is addictive as hell to play in LAN parties. I recommend it to everyone that loves shooters and want to try the arena shooter genre.