Alcatraz

'Sliders' (1995-1997, FOX; 1998-2000, Sci-Fi Channel)

Here's yet another show that started promisingly but ended, eventually, on a sour note. Things got so silly that you really couldn't blame star Jerry O'Connell for walking away before the final season. (Eventually the show's ... more producers replaced him with his brother, Charlie, who was a less-than-charismatic lead.)

That being said, "Sliders" did start out on a fun note and the show clearly understood the possibilities of time travel. The idea was the characters used portals to "slide" into alternate realities, sometimes shifting time periods as well.

The self-contained episodes were among its best. Trying to develop a story "mythology" -- the Sliders were trying to prevent evil aliens from wrecking the "multiverse" -- was less successful, if a noble attempt to make the series more coherent and cohesive.

(Sci-Fi Channel)