The Diablo was actually more of a hypercar in the 1990s than the early Murcielago was in the early 2000s. The SE30 and SV twins were surprisingly as fast, if not faster than, the Ferrari F50 and quicker than the Bugatti EB110GT; just slightly slower than the EB110SS and XJ220. The Diablo went directly against Ferrari's halo cars; the 5.7-liter versions went against the F40, and the 5.7-liter post-facelift and 6.0-liter versions all went against the F50. The Murcielago still took the lead in 2001 (it competed against Zonda and Saleen S7 but at a much lower price), but it got overshadowed pretty quickly by the Enzo. LP640 did make up for it though (albeit on the level of Carrera GT, SLR McLaren, Ford GT; as opposed to the more extreme side of hypercars: Enzo, EB16.4 Veyron, McLaren F1, and Koenigsegg CC). The LP670-4 SV was the Enzo/EB/F1/CC competitor, though. Still, the (Murcielago) SV is nowhere near the rare homologated track beast that the Diablo GT is. The GT was the replacement for the (Diablo) SV, as well as the predecessor to the (Murcielago) SV. The GT has a top speed very close to that of the Enzo's, and even the 6.0VT has a higher top speed than the early Murcielago.
I like the Diablo better than the Murcielago.
NEITHER car is as iconic as the Miura and Countach. Those ruled the supercar world in ways that Ferrari never (really) could. They made Ferrari look more like an Aston Martin or Maserati on steroids.