I've had very few lenses that underperformed to a degree that I can clearly blame the lens
and I've bought and sold many in the past four years, including several I've tried more than once (16-45, 18-135, 18-55wr). The ones I would refer to as my 'best' were the Sigma 105 macro or the 40/70 Limiteds, and I have not repurchased any of them. My best lens today is probably the A50/2.8 Macro, and I'd miss it a lot - but if it vanished I might buy another 40 Limited and
that would become my best.
My lens set always has been very context-dependent, and right now my primes are all manual-focus bargains with large but not huge spacing; adding a few great AF primes would probably knock over all the dominoes and start me over on a new path!