I feel like you would want quality, but if limited to three full series, you'd pick long ones, right?
  1. The West Wing - BEST. SHOW. EVER. I can't pick a favorite character because I love them all so much. Except it might be Toby. Or Charlie. Or CJ. Gah!! See? Impossible to choose. Brilliant writing, amazing cast, inspiring and enlightening and just the best thing ever to be on tv.
  2. Buffy the Vampire Slayer - almost, almost the best show ever. Epic plot lines, clever, badass female characters, the feels - all the time, amazingly quotable dialogue, many quips and puns, 90s hair and clothing. I graduated the year Buffy did, and I loved this show to an insane obsessive degree. And true love lasts forever
  3. Friends - I would need a comedy to lighten the mood occasionally, and despite the dated clothes/hair/pop culture references, it totally holds up. Still funny!