Genshiken, Boku wa Tomodachi ga Sukunai Recommendations
* Both are about a school club and making friends in the club.
* Both have a basement in their club and attend it almost all the time.
* Both have the same feeling and vibe to it.
* Both will leave a very similar impression on you.
* Both are erotic but Haganai is Ecchi and Genshiken is not.
* Both have Otaku/Gamer characters.
If you liked one, you'll definitely like the other, I have given both of them the same score.