i will tell my story i use a lot of online gaming programs ( Gameranger , Garena )
i was using this stink internet that give 1/10 of the speed i was paying for but the online gaming speed was awesome !!!
now i use another ISP who give me 9/10 and it is unbelievably slower !!!!
how did that happen !!!

contact your isp and tell them there's a problem. 9/10 times they'll fix it
i can't just tell them "my gameranger is slow but i have full speed in other stuffs ! "
hmm looks like my connection is not stable enough !
anyone had this problem before ?
For gaming the speed doesn't matter too much, what's most important is ping. You should run a speed test with a server close to the people you typically play with and see how long it takes to ping. For lag free gaming you'll want to be under 20ms
yeah i totally get that but the worse thing i had even if i am playing with people around the globe is delay but now it is like putting frame skipping to skip 30 frames in PCSX2

I have lousy ping also sometimes.But whenever it's ISP working hours it's normal ping

I'd go to another ISP then, ask around with your local friends what kind of pings they get with DSL, Coaxial, or fiber.
*would post speedtest and pingtest resutls here, but not at home*