You would say "back in XXXX" to emphasize that it happened some time in the past. Otherwise there is no difference in meaning.
I graduated high school in 1984
I graduated high school back in 1984.
You can also say "way back in" to emphasize that it happened a (relatively) long time ago, as if it was ancient history.
I graduated high school way back in 1984.
So with regard to your example,: saying "EVE Online launched back in 2003" emphasizes that the game has been around for quite a while. This will usually be I expect this is relevant to some other point mentioned before or afterin the article -- for example that, as a result, the game is polished, or has an established player base, or that the developers are committed, and so onor something similar.