Like Enterprise, the last two movies didn't exist. Its easier that way.
Enterprise got really good the last couple seasons, and the first two weren't any worse than the first two of any other Trek series. It gets a ton of **** it doesn't deserve.
Enterprise is my second favorite Trek series behind TNG. And even TNG had an uneven first two seasons.
The problem with Enterprise was a bit of its premise. It is the beginning of deep space exploration. I think the first season did a good job of showing what that would sort of be like in a universe full of other alien life forms. The problem is that it isn't always that interesting to see these characters encounter things we've seen plenty of times on past series as they begin to progress in meeting other species or planets. As well, they make decisions that can seem stupid when we know the protocols that will be enacted in the future to prevent such decisions and so it doesn't help when comparing it to past entries yet it makes sense in that world.
I think of a scene in the third or fourth episode where they come upon their first M class planet. The crew is all excited to discover a new habitable world they can visit so they go down in the shuttle and they're all wearing these Starfleet hats and taking pictures of themselves on the planet. It's a bit like sailors on shore leave but at the same time it makes sense for them to have this reaction in that universe. Of course, they later have issues with the air on the planet and that is a bit of the plot. You compare this to TNG where an away crew beams right down to a planet and it is all business and they've got tech to scan the environment and look for dangers. Over time, the Enterprise crew also gets down to business but it does make it fill like filler or rather pointless when first watching the show.
In past Star Trek series, contact had already been made with Klingons, Romulans, etc. Those conflicts didn't require much set-up. With Enterprise, we had to see them encounter all these races the first time and start to sow the seeds of why relations with these aliens is the way it is on past Trek shows. After the show got through a lot of these "first" time moments and set up and starting establishing a lot of Trek politics/relations and focusing on those, it was as good a Trek as any. I'd say from the midway point of Season 2 onwards it is worthwhile with the occasional stumble / boring episode that plagued every Trek series before as well.
It's that early initial set-up that I think hurts the show for anyone that wants to get into it. It was clearly done purposely like that, however, it might have been better to start the series at a different point in time like having a new crew member come aboard the Enterprise after it had been out for 2 years as he learns what they've encountered and gets to know the crew and cut out some of the early growing pains. You could still have the wonder of first time deep space travel with the new member contrasting it against the veteran crew that has been a bit hardened by their travels and get the best of both worlds.
In the end, Enterprise is the only Trek series I've watched all the ways through 2 besides TNG so it still appealed to me and I find it more watchable then the Original, DS9 and Voyager. I also didn't mind the theme song.