Basically it does sound like there is an issue but it could be your internet or the wireless.
In general wireless is always worse because devices have to take turns to talk, this can include your neighbors if they are using the same wireless channel(frequency) as you. With wireless g/n(2.5ghz) you are limited to 3 frequencies which don't overlap (channel 1,6,& 11). You can download a free program called inssider, which will let you see everybody's wifi and the channel they are using, to see if there is one free you dont have to share, but chances are there wont be, so if your neighbor starts using their wifi for watching netflix etc the time your device has to wait for its turn to talk shoots up and you get latency.
You can see if this is the issue by doing the following: next time you lag turn off everything that uses the internet including windows update, start running continual ping tests to your router/default gateway. (open command prompt and type "ping -n 100 -l 1000 [ip address]"), if you regularly see high pings you know there is a wireless issue.
The other explanation is there is contention on your internet conenction, once you know you are latency free on your wifi, or ethernet cable, you can run the same ping test between you and your telephone exchange to see if there is an issue there. Run a traceroute to anywhere on the internet.. eg tracert www.bbc.co.uk, the first hop you will see is the ip address of your router, the 2nd hop you will see is the ip address of the telephone exchange. Ping that