[Help] Ping Spike

Ever since a few years ago my internet would lag like someones decided to change it to dial-up. I have have ADSL 1 which downloads at a fair speed of 150kb, Australia doesn't seem to have great internet (we use to have ADSL 2+ but we changed it to ADSL 1 due to the fact that none of us really needed the extra speed)

Alright, anyway if I download, watch movies everything is absolutely normal but if I play any game my ping would spike up to 700+ I mean my internet is slow compared to other people but 700+ is a bit excessive? Because of that I stopped playing games like Gunz, Rakion, etc the only game that ever worked was Gunbound and I STILL lagged on it. Now I'm playing Runes of Magic and my Ping would be 700+ does anyone know why? is something wrong?

Ahh, and another thing, if I connect on a CS game my friend makes, I would also have like 700 latency, same case if I host the game (they get the high latency and I'm fine)

If I can remember my internet speed is 1500/256 download and upload respective, It would be fine if it was because of my internet but I still can remember when it USE to work and I never bothered to find out why suddenly everything stuffed up. And during that time I've used a different router, a different wireless adapter and even a entirely different internet.