Bad internet only when playing videogames

Okay SPEED does NOT equal PING response. PING (the 1000ms lag) is how long does a signal from A to B take then from B to A. So like a car, you can be 75MPH on the highway, but as soon as you get on the offramp, boom stuck in rubberneck stop and go traffic, doesn't matter how 'fast' the highway was, your still got slow down on the 'connection' / road.

Now that you did see your 'not' getting the expected speeds, lets properly test this;

That is the first thing. Unplug any other computers, leave just your computer plugged in, and turn off wifi.
Now use the router built in webpage (usually your IP like 192.168.0.x but replace the x with a 1; check the included manual with the router OR go to the manufacturer's webpage and download the PDF manual and read it there) and there is usually a diagnostic / test page you can test the speed, and see what it says.

IF with a single wired computer and NO OTHER DEVICES (no phones, no consoles, etc.) and your speed stays that low, call the ISP, tell them EXACTLY the steps your doing right then (explain it in detail as I did) and how your speed is. The issue would be with your ISP

IF you do NOT have a Diag/Test page, then try with the single computer, then unplug it and try a different computer. If both computers WIRED one at a time, both get bad results, again tell the ISP what you did and how you tested and results.

IF the speed is good on ONE computer but NOT the other, then the issue is with the 'bad' computer only.
If both are good, then lets test Wifi, turn off any other cellphone/playstation/tablet whatever that is wifi (or just disable its wifi for a couple minutes). Now use one computer WIFI, test your speed. Now turn off wifi on it, and test with a second computer.

Again same logic; If one computer works but not the other, then the 'bad' computer has the issue. If both work fine and speed is fine then the next would be to test when 'farther away'. Do you see ALOT of wifi names in your list? IF SO then you need to change the Radio Channel to keep from getting interference from neighbors, AND make sure the NAME of your wifi is unique (My neighbor's is called Netgear, and mine is called Netgear OH DANG which one is my computer connecting to??) to avoid confusing the WIFI.

Then once you tested it to 'where I like to sit all the time', and still all good, start turning on WIFI / plugging in other devices. You can plainly have Little Sister Torrenting the entire LOTR series for the past week and well that be why your speed is so low. REMEMBER: It is NOT 25Mpbs TO EACH COMPUTER, it it 25Mbps to your entire HOUSE, with ONE computer or 392 Smartphones being used. Too many devices or too many people doing streaming will 'lag' spike gaming.