Thought this might be useful. This is based on US TV premieres for April. Let me know if there are any omissions.
I threw in a couple of cartoons but it's not exhaustive.
Total Riff Off
NGEO - The RiffTrax guys (MST3K alum) take on Nat Geo specials
Season 3 SYFY
Game of Thrones
HBO Season 4
Robot Chicken DC Comics Special II
ADULT SWIM - Stop motion silliness
DISNEY XD - "Guardians and Space Knights"; Cartoon; Might be of extra interest with the upcomings Guardians movie
HULU - Supernatural comedy series with Tyler Labine
SYFY - Saturday Night Movie with Linda Hamilton
Hulk and Agents of S.M.A.S.H.
DISNEY XD - "Deathlok"; Cartoon; Might be of extra interest for those watching Agents of SHIELD
Metal Hurlant Chronicles
SYFY - The final six
BBCA - Season 2 Premiere
Bad Ass Spider!
SYFY - Saturday Night Movie with Greg Grunberg and Ray Wise
NOTE: Not listed as a Syfy original, might be decent dumb fun?
The Real History of Science Fiction
BBCA - Four-part documentary series
WGN - WGN throws its hat in the ring with its first scripted show from Brannon Braga