This was me as well
I picked up BFBC after never properly owning a Battlefield game (due to owning a shitty computer) but playing many at internet cafes etc. I fell in love with Call of Duty 2 and 4 but upon Bad Company 1's release i played it for hours. I still miss the 'End of the Line' level from BC1 as it had so much variety and action.
Never the less just like everyone i rode the Call of Duty train but made an oath to pick up BC2, at first i didnt enjoy it that much especially since MW2 was released around the same time but ill find myself constantly coming back to it just from the thrill of blowing up a tank or tagging a helicopter with a tracking beacon then quickly firing a RPG at it to see a beautiful display of fireworks.
I can now finally say that i am a huge fan of BOTH series now, and i love that both exist and will continue to hope to 'best' each other and improve upon themselves. Call of Duty is an arcade, fast-paced shooter and it succeeds amazingly at being that; Battlefield is a realistic (to a degree) tactical, vehicle and objective based game that strives on teamwork.
Welcome to Battlefield!