Well I'll be more fair to the seriesessesss..
TOS: It obviously established the Star Trek universe and gave us some great characters (Kirk, Spock, Scotty, Sulu), even if they were over-the-top or just plain ridiculous. Stories were good because Gene Roddenberry was a genius who was actually trying to make social commentaries about the upheaval of the 60's.
TNG: Yes, the first 2 seasons or so were a little rocky, but still fairly solid (except for Shades of Grey..the one where Riker has flashbacks). But the acting and storylines from this series were amazing. Patrick Stewart and Brent Spiner are two of the most amazing actors and they just played both of their characters extremely well. I just think it went one seaon too long. Thank god they did the finale right, though.
DS9: This is probably my second favorite series and I really liked everything outside of anything to do with the Prophets/Kira/Bajor exclusively. Quark is the man and this show probably had the best comedic moments overall. Another thing I really liked was how later on it showed the dark side of the Federation/Starfleet that wasn't really shown before, or really since. The ending, as I said, was just plain ridiculous.
VOY: When this first came out I thought I was going to hate it. But it really surprised me. I really liked the characters (especially Tom, Tuvok, and the Doctor especially), and the originality of the setting and villans/friends. Kes could have been completely written out of the show, imo lol.
ENT: I actually really liked this show. Alot of people give it flack for not being entirely canonical, but I just thought it was a really good Star Trek show. It was pretty cool to at least see the early times of Starfleet being depicted even if it wasn't entirely on-line with what was in the other series/movies.