I'm enjoying DSC a lot so far. On an episode-by-episode level, I think its first season is neck-and-neck with TOS's so far. BUT the focus of DSC is way too narrow. It's just about the Klingon War except for the detour into the Mirror Universe. The other series all had a broader range of stories. DS9, like DSC, was also serialized but it managed to juggle a lot of material all at once. The original Bryan Fuller pitch made DSC seem like it would have a gigantic meta-focus and, through shake-ups and changes in direction, that's become lost in the translation.
The other thing to consider is that while I think DSC has had a great first season, what if I end up in a situation where -- three years from now -- I'm wondering why DSC still can't have the same quality it had in its first season? I thought BSG had a near-perfect first season. The second season slightly less so. The cracks began to show during the third season and then it went right off the rails in the fourth.
If DSC can keep up where it's at right now for at least a few years, or do better, and expand its canvas, then I'll be at a point where I'll able to seriously wonder, "Do I think this is the best series?" At this point, I'm just really enjoying it and am happy to leave it at that.