I did like it a lot but best story DLC is a stretch I'd say when we have Seperate Ways, and Lost In Nightmares which are both fantastic. That being said I would definitely say this is in the same league as those and I could potentially agree as far as telling a seperate story that this one could be the best even if it's not my favorite.
Not a stretch in the slightest.
Separate Ways was just more RE4, which is good and fine in itself, but really, what was so special about it? It was a nice chunk of extra game time. Outside of that, there's nothing notable about Separate Ways except for more Ada and an alternative perspective to the RE4 storyline with tidbits of additional lore that was largely dismissed when Capcom decided to create the narrative mess that was RE5 and ignore Ada and Wesker's developing plot in RE4 anyway. It simply provided more of what we already liked about RE4, but nothing truly meaningful or substantial on any front. The gameplay was near identical, too. Separate Ways has more potential to be something unique with the remake coming, just as the main story of RE4 itself does, since Capcom's narrative chops have been much better lately.
Lost in Nightmares was a poor attempt at recapturing traditional survival horror during a time that Capcom had no idea how to make a Resident Evil game, after completely derailing the series on every level with RE5. I hate Lost in Nightmares with a passion because it felt like they were just pandering fan-service to the survival horror crowd that they've no longer understood or cared to understand any longer. It was a cheap, tone-deaf knock-off that lacked originality or level design. It was terribly short, too.
By comparison, Shadows of Rose provided so much more of an artistic identity. New gameplay twists, a meaningful environmentally story-driven narrative and much better character development/writing than anything Separate Ways or other post-release content provided. Village now in hindsight feels "complete" and less flawed because of it. I'll also mention the doll house again as being one of the most well-crafted horror sections I've ever played in a video game. It also had a lot more heart, in my eyes.
It wasn't a perfectly designed experience, but Shadows of Rose should be seen as the standard.
Aside maybe some of the RE7 Story DLC to a lesser extent in its bite size chunks, nothing came even close to the quality of this DLC in the series. Period.