I like all incarnations of Star Trek. But, regarding Enterprise...

Star Trek: Enterprise never really felt like the Star Trek we all know and love.  They really strayed in this series. One of the biggest complaints is the handling of Vulcans. In my opinion, the Vulcans of this time haven't gone through their second awakenening/enlightening as a people. Too bad it never was explained.

Out of the entire show, I believe these are a great lead-in to the "later" shows.  These are the episodes I would only recommend watching.

Season 1
Broken Bow
The Andorian Incident
Fortunate Son
Dear Doctor
Shadows of P'Jem
Shuttlepod One
Fusion
Vox Sola
Fallen Hero

Season 2
Carbon Creek
Minefield
Dead Stop
The Communicator
Stigma
Cease Fire
Judgement
Cogenitor
Regeneration

Season 3
E2

Season 4
All but Storm Front 1, Storm Front 2, and These Are The Voyages.


Now.. quick commentary on some of my choices.

Minefield
In my opinion, one of the best. Great intro on the Romulans.

Judgement
Another good episode, adds new insights into the Klingons.

Regeneration
I'm reluctantly recommending this one. It's a Borg episode. They don't announce themselves by name but it is a decent sequel/prequel (don't get all timey whimey here!)

E2
This feels like a Next Generation style episode, it's the only really watchable episode for Season 3.

These Are The Voyages...
In the final episode, they show the signing of the Federation charter. Which is regrettable because I consider the whole episode REALLY tacky. The writers meant well and for me to say that the execution was.. poor.. is putting it way too politely and should tell you something. But at least it's not "Spock's Brain" from the original series.. lol