Here, enrichments A and B look excellent, while C and D are not quite clear.

A and B look excellent because your most important variables (indicated by colour, with black being most important, and light grey being least important) are positioned at either the left- or right-most part of the plot; moreover, the density of important variables is also high at both of these locations. The enrichments in A and B are going to be highly statistically significant.

'Importance', here, is gauged by whatever is your input data, which may be expression level, fold change, negative log10 p-values, or something else. Further, the directionality of this importance is indicated by the coloured horizontal bar - if fold changes are the input, then red equates to positive fold-change, while blue equates to negative fold change. Thus, we also have information on direction of enrichment. In A, we can infer that the PRONEUAL_PHILLIPS signature is activated, while, in B, PROLIFERATIVE_PHILLIPS is deactivated.

C and D don't look too great, in part due to these signatures being small in size and there being no trend or consistency for your variables. C undoubtedly scores better than D, though.

Kevin