I listed M:TW, M:TW-VI, R:TW, R:TW-BI, and M2:TW.

I first got into this series hearing through word of mouth about what a great game Medieval: Total War was, and I bought it and was quite impressed, growing very absorbed by that game. Consequently, I've collected each new game and watched the series grew in popularity. I didn't get a chance to buy Rome: Total War-Alexander, and Medieval 2 came out soon afterwards, so when I was in a position to get a new game, I opted for the newer one.