Wi-Fi is rather notorious for being susceptible to interference (they're just radio waves, after all). Here's a small checklist that you should go through to make sure you're doing everything you can to reduce interference:
- Place your wi-fi router at an elevated place, away from sources of interference (such as TVs and soundsystems, as these have been known to cause interference).
- Move other wireless devices (phones, tablets, etc.) away from the router
- Play around a bit with the channels: though it should be set to "auto", a neighbour's wi-fi may be interfering with your own, causing delay and packet loss. If this doesn't help, you should put the channel setting back to "auto".
If nothing helps, you'll just have to somehow get a wired connection to the PS3. Your other devices probably don't need as little delay that the PS3 online games require to be played with no noticeable problems, hence why you're not experiencing any issues on them.
Quick edit: A difference of 103ms vs 36ms using the same router is pretty big. I don't know if consoles are known to have slightly worse network capabilities, but it also seems like there's some interference, or it might just be that the PS3 is too far away from the router.