Yeah, first couple seasons are notoriously spotty, partially due to Roddenberry banning any conflict between main characters. I've watched the show totally out of order and there's tons I haven't seen. I think if you're not really invested in the show you'd be fine with one of those best-of lists.
Deep Space 9 is a lot more interesting as a show, it really pushes back on a lot of the utopian hurray-for-humanity stuff that can be grating on TNG. There are several episodes that get to a level of darkness that TNG approaches maybe once (in the famous Picard-gets-tortured episode).