As you have mentioned, the best way to evaluate a scholarly article is through subjective evaluative comments. However, it might be difficult to compare articles across fields solely on the basis of such comments. I am not aware of any resources as such that might help compare studies across fields, but you could consider a few things apart from the subjective assessment:
- You could consider which journal the article is published in and what is the standing of the journal in the field: whether it is among the leading journals in the field, or a relatively lesser known one.
- You have mentioned the total number of citations. Along with that, you could also consider the Altmetric score of each article. The Altmetric tool measures the number of times a research output gets cited, tweeted about, liked, shared, bookmarked, viewed, downloaded, mentioned, reviewed, and discussed.
- You should focus on the impact of the findings of each study; for example, how significantly they contribute to the field, whether the research is groundbreaking or highly impactful or is simply building on an existing line of thought, etc.
- Additionally, you could consider involving a few experts from multidisciplinary fields as they might be able to compare the impact of studies from different fields.
I hope this answer helps.