[{quoted}](name=gas reformed,realm=NA,application-id=6kFXY1kR,discussion-id=qtERa5Uv,comment-id=00000000,timestamp=2017-02-07T02:14:51.623+0000)
More colors and details in comparison to new, obviously. Also, the music from those trailers alone have a better feel than the overdone stuff of today.
The music is different because it's in an edited trailer, this was never the actual in game music (The old in game music is actually still available in settings, you can check it out).
The game was recorded in highest settings (for trailer), thus have good details. If you turn up the settings in your graphical settings, it should look more detailed since the texture resolution, animation and particles have been improved a lot. You should not compare a game on lower settings to trailer video on high settings.
In terms of the graphics feels more "popped", it was because the old models and maps used more spikes and colors with stronger contrast . It was designed to help the graphic stand out in lower resolution, poor color gamma displays.
Since consumer computers are getting better, Riot has shifted their design to feature more polygon since then. Maps were made dimmer to make the particles stand out so players can see skill shots better.
It was a move to reduce "visual noise" on screen. Some people may prefer the older style on this issue. But the rest should be improvements on a technical aspect.