Lonerism is certainly better to my ear musically of the four albums. But I'm not the demographic, so I'll just drop some irrelevant Robert Christgau-level old guy pontification...
While the difference and relative importance of Lonerism vs Currents vs Slow Rush doesn't really approach the Bends vs OK Computer vs Kid A path, I imagine someone in their 20s now would go all oooo and aaah about TI the same way kids in the late 90s did over Radiohead. Personally, I hated Kid A and still do.
The first three Tame Impala albums to me seem more like Parker/TI is progressively doing to the Beatles what PM Dawn did to hip hop back in the early 90s, with the difference being I found the latter to be lyrically uplifting.
Which is not say Parker isn't immensely talented. There are some great riffs in the earlier work along with some remarkable bass lines and leads. His technical detail is certainly good, and you can sense he's after studio perfection, but I just can't get all worked over about executing drum fades.
OTOH, I learned he's a fan of Serge Gainsbourg which makes total sense. And the opener to Lonerism, "Apocalypse Dreams" sounds like something you'd get if Gainsbourg was leading the Polyphonic Spree.