Plenty of reasons! The atmosphere of an old school RPG is very strong in Genesis, even though some players obviously treat it the same way as new age mmorpg games. I mean if you enjoyed MERP or WHFRP, Genesis has similar feeling when you play it.
A Polish rpg-fantasy gamer can learn english this way - and there are most of the main fantasy domains in Genesis - everyone can find something for himself there.
The community here is great - the way people share their opinions, their attitude, how problems are solved, they way all things work here - it's quite unusual and of high quality. It takes not only time to create such community but also a real passion for what you do. It's great to be part of such comunity, and this as well gives very unusual opportunity to learn english.
All Genesis is filled with knowledge, books and a lot of good work, so even if you don't feel like really playin the game you can spend hours venturing in the libraries (and sometmes you need to spend months to get to some in-game libraries).
And Moderators, all the Wizards are great - you have such open and welcoming attitude towards players, you share your opinions, you care about the game and the players. You can't find it anywhere, it's a great advantage of Genesis, as Wizards are the most important players (and creators) of the game.
Even though there lacks hands to work, something is always going on. Polls, changes, guilds are being updated, the progress is shared with players. And events that is something very amusing, and I'm sure it will be for Polish players.
There are literally tons of reasons to play genesis, I could write a book about it

B.
(sorry for mistakes)