For basic editing, you already have the best. For pixel level editing, and professional retouching and manipulation then Photoshop is the best there is.
It depends what you want to do. If all you want to do is adjust the levels, tones, maybe remove spots and imperfections... darken skies, adjust colour etc.. then Lightroom can do all that, and what's more, it does it with teh RAW file if you want it to, so everything is reversible.
You want complex image retouching, manipulation, ability to composite images, or do complex airbrushing etc, then there's nothing to rival photoshop.