Quick answer: There are many nicer books on the Strip (and off-Strip).
Longer answer: Here's a quick review of the sports books I've been to downtown:
Plaza (Lucky's) - Haven't been here in awhile, but it was pretty nice when I was last there. Is it still open? Most of the casino isn't.
Golden Gate (Leroy's) - Just a kiosk for self-made bets. You can do better.
Golden Nugget - Haven't seen it.
Four Queens (Cal Neva) - No TVs, just a couple of bet takers. Can sit in the keno lounge nearby.
Binion's (Cal Neva) - Haven't seen it, but I've heard it exists.
Fremont (Boyd) - Electronic odds boards, some TVs, not much seating, can get crowded & smoky at times.
Fitzgeralds (Lucky's) - Upstairs, small, just bet takers and maybe a couple of TVs. Prefer others.
El Cortez (South Point) - Not half bad, if you can stand the clientele, the smoke, and the perfume.
I wouldn't call any of these places "fun" or "comfortable", though some of the locals can be very interesting to interact with. At the Fremont and El Cortez, you need to bet to get drink tickets (something like $20-40 per ticket for both places), though it's possible to get served without one.