Nothing is as good as Tenergy. Tihar Evo MX series comes closest.
That's a recognizable story, but I think it applies to the non-"FX" tenergies. People are looking for less expensive alternatives to T05 and tend to come up short, because, well, different rubbers in the end feel differently.
I don't think the "FX"es are that special, that is to say, to me the feeling of the T05FX rubber isn't that unique. The good things about it can be had in other rubbers — Rasant Grip, for example, and now Rasanter R42, and Rakza 7 Soft, and a lot, lot more soft- to mid-hard tensor-types like it. It may be me, but I didn't find the spin-intensive qualities of T05 back in T05FX either.
Actually, Butterfly happens to offer a rubber that sits squarely in the same family and shares quite a bit of the "tenergy" feeling,
and is less expensive; Rozena. Slightly less spinny, slightly less speedy, slightly less bouncy — and all of these are probably a good thing for a good many players.