ANA. I have both Sylenth and ANA and they sound quite different even on similarly designed patches. Ana is brighter and thinner, i would call it more modern sounding. Sylenth is darker and has more weight in sound. I like ANA for electro-dubsteppy wobley stuff and prefer Sylenth for supersaws, plucks, huge pads and 303ish sounds. BTW, ana has much more osc waveforms than Sylenth hence sonic pallette is potentially wider.
DUNE. Only demoed it. It also sounds different than Sylenth, more mellow. It somehow lacks Sylenth's bite. DUNE seems to be pretty well suited for chilling/ambient productions but not so much for trance or other EDM styles.
Saurus. Demoed it yesterday and was very impressed. Like Sylenth it has very strong, alive and pleasing sound, but with different vibe. It seems to be very limited synth, just plain subtractive architecture, but on the other hand very easy to program, and any knob movement makes some pleasing result (also demoed their Electrax and strangelly did not love the sound. There are some similar factory patches in both synths, and comparing them side by side I always felt that ElecraX lacks something improtant, that Saurus has and proudly shows)
Z3ta+ Very old synth (2003 or so), recently reissued. Before Sylenth it was a staple for ITB transe producers. Sounds kinda lo-fi, but that may be called "character". It can make some very lovely transey sounds but is tricky to program.
LUSH-101, Diversion. Both sound amazing but barely usable with such CPU load.
Never liked any of Rob Papen synths.
Having thus said, if you vant THAT Sylenth sound (which is really that good)just by Sylenth. No other synth can 100% replace it. The development actually seems to be stopped but the product itself is mature and well supported and updated at least on Windows (Mac guys seem to be not that lucky)

