The reason Sarkeesian is terrible:
Her "well-researched" video series made for over $100,000 donated by her fans, large sums of which were donated by suspicious accounts or by accounts owned by her personal friends, are incredibly short and incredibly basic videos by youtube standards that absolutely anypony with a home greenscreen setup and a decent video camera could have made in a couple days at most, and are full of hilariously inaccurate, completely nebulous, or just plain meaningless "facts" that in no way support her claims.
Also she stole most if not all of her video game footage from youtube LPers and never actually credited the sources.
Also she's not a video gamer and doesn't even like video games. In her own words. Repeatedly. At many, many of her seminars and appearances before she decide to suddenly be a video games expert.
Moreover, Sarkeesian in no way actually attempts to debate any of her points. She states her own personal opinions as absolute fact, does nothing to actually argue those opinions, gives no open forum for anypony to disprove or counter those opinions, and has had a long ongoing campaign of censoring any evidence against her. Her vast claim of the entire video game industry being an evil "boys only club" is supported by a minute handful of cherry-picked examples taken grossly out of context, most of which are represented in a wholly misleading fashion or just plain incorrect altogether.
She's a con artist and she's getting away with it, and in the process she's become a huge figurehead for "feminism" in the eyes of the mass media, doing arguably more harm to the cause she claims to support than if she'd never existed at all.