Sense of family and homeliness. Humor.
To start with two stereotypes, TNG characters are often almost too perfect, DS9 were cast in a very "grey" universe with big moral struggles to which there wasn't always a clear-cut answer.
In Voyager, the balance was between those two and tuned down to a more 'homely' scale. I mean, sure, there were big battles and decisions with galaxy spanning ramifications, but a lot of the times, those moral dilemmas often were the kind of stuff we all have in our daily lives - neither the perfect universe of TNG nor the epic struggle between good and evil with grey areas with no clear cut answers as in DS9 -- in VOY you often knew what they "should" do, but still have problems with it because of their personal flaws, which actually resembles most of the situation I encounter in my day to day life.
A different dimension of this 'homeliness' was that they literally had to build their own community, their own sense of home, since they weren't expecting to see their real home for another 70 years. In the better episodes of later seasons, a sense of family really pervaded the 'feel' of voyager. Also, the humor, the kind of pranks or quips they liked to play on one another, or everyone gladly suffering the grandiose ego of the EMH, for example.
Also liked that they did some experimenting with episode formats. Muse is an interesting example.
(and yes, VOY also had some notable flaws, but this thread isn't about those).