Season 1 of ENT combines a few story arcs with Scifi/adventure/action episodes and character episodes - but the Scifi/adventure/action stories are mostly weak, and you feel like you've already seen them on other Trek shows (this is also the case with VOY). It gets worse in season 2, when the network ordered Berman & Braga to lay off the show's arcs (Temporal Cold War, Andorians and Vulcans) and do more episodic Scifi/adventure stuff, something that never really worked well on ENT. As for the arcs, one of those - the Temporal Cold War - was never well planned, and was never resolved in a satisfactory way. The Vulcan/Andorian stuff, which leads to the birth of the Federation, was better and would continue in season 4.Where would Enterprise fit in here, I've only watched one or two, but that will be next after Voyager... does that follow more after DS9 as character based, story arcs etc or more scifi adventure and action based?
There's character development, but in the early seasons there is some inconsistent writing for the captain character (which is also VOY's problem). A lot will depend on whether you find the characters engaging or not. If you like them, like I did, it will get you through the weak and average stories. If not... I doubt that you'll ever really enjoy the show, and you certainly will find a lot of the first 2 seasons unbearable.
Seasons 3 and 4 are very different than the first two - and much better. Season 3 is build on a year-long story arc (which starts in season 2 finale), features conflict on the ship and takes the characters to dark and difficult places. One could day that the first 2 seasons, especially season 2, feel more like TNG-lite/VOY, while season 3 feels more like DS9 in its later seasons or BSG. It also features some great action/battle scenes and, something I was especially impressed by, some of the most amazing visuals in Trek - instead of technobabble, you get to see what "anomalies" can be like, and generally, it does a good job of "show, don't tell".
Season 4 is the season where ENT really started doing what it should have been doing as a prequel show. You get a lot of references to TOS and other Trek shows, and it consists of a several storyarcs, including a few 2-parters and 3-parters, mostly dealing with politics, Earth's relations with other species, origins of the Federation, etc. However, the finale "These Are the Voyages" is horrible, feels completely out of sync with the season, and pretty much everyone now sees it as a mistake.