Hey i was looking for exactly the same as you mate and like you i played on runescape for since near the start (05). I believe i have found an alright game that you may enjoy which is conquer online. I know it has alot of bad ratings on site (maybe for graphics) but the gameplay is very much like runescape the download is only 500MB! On average take about 1 hour on 250KBS. you can download at
http://co.91.com and if you enjoy the game you may want to get a private server (VERY FUN!) hope you play it and enjoy it :-)