As of Glob's contribution I'm starting to warm up to the franchise.
Being a "trekker" myself, I must say that the franchise sure has it's ups and downs. It's very long franchise after all, comprised of a ton of different shows with separate casts and characters.
I classify them as follow (personal opinion of course):
TV:
Original series: Nice charismatic main characters, but quite poor (it's low budget and from the early sixties... very cheesy, sometimes cringe worthy)
Next Generation: Not my favorite, but quite good overall.
Voyager: Probably the weakest (except for the original series), but not as bad as they make of it.
Deep Space 9. My personal favorite, best stories overall, best overall assortment of secondary characters. Reminds me in times of my favorite scifi show ever, Babylon 5.
Enterprise: Another of my favorites, but the final season was poor.
Movies:
Star Tek (the first one): No big deal.
Wrath of Khan: Not my favorite, but good.
Search for Spock: One of my favorites.
The Voyage Home: Probably the cheesiest and overall one of the worst.
The Final Frontier: So-so, better than A voyage home, but still worst than most.
The Undiscovered Country: My favorite of the bunch. A hidden gem.
Generations: So-so, the transition movie from the Kirk era to the Picard era.
First Contact: Nice
Insurrection: Quite poor.
Nemesis: Pretty, but ultimately just so-so
All the movies by JJ Abrahams: Pretty but junk. JJ completely failed to understand what Star Trek is about, so he made Star Trek movies for Star Wars fans, ending up with a bunch of movies that are as much Star Trek as I am a Galapagos Turtle. Star Trek was never a high paced, acton packed adventure thing, it was a journey of discovery, an exploration of "what-if" scenarios, "how would it be, what would we do", and ultimately a way to explore humanity itself using space travel and other species as an allegory to explore facets of ourselves, a journey of introspection disguised as a journey of discovery.
There is truth in your words.