I’ve been wanting to make some more kinds of sfx, particularly sfx for things like on videohive and things for people to use in their songs like dubstep and stuff but out of like 20 supposedly “top” synthesizer plugins I’ve tried, none of them are at my standards of quality, they all lack a professional sound I’m use to working with. Steinburg didn’t cut it, splice wasn’t good enough, spectral wasn’t good enough, synplant was unique but too low quality. I’m looking for something that focuses on high quality sound over some pretense of being analogue and having 50 oscillators at once. There’s no such thing as analogue on a computer, the best synthesizers are going to be by those who admit they don’t have an analogue synthesizer and work with the digital system they have.
Serum from Xfer records is your best bet. It can generate amazing dubstep and drum&bass neuro sounds as well as punchy FX’s. In fact , many dnb, dubstep and complextro producers are using it. There are also many preset packs you can buy for it. quality is top notch.
Sylenth1 by Lennar Digital. It’s a legend)
Agree, it’s absolutely brilliant!
Serum has lots of modulation options, its really good for dubstep and experimentation, also Ill vote for Omnisphere 2, it has granulizer and its really cool to use it for SFX. In both synths you can load ur own waveforms 
Remember, synths just generate a tone. Its how you process the sound after with effects like distortion, reverbs, filters, waveshapers etc will make your final sound. You can achieve anything with any modern synth if you know what you doing.
I use KORG Triton for a long time. Very pleased with the results, especially when I need “space and technology”
I’m not Serum user, but seems like it’s a winner nowadays.
I stick to good old Massive, FM8 and Reaktor, but frankly speaking, best effects I got from granular synthesis, warping and resampling.
Wow, i remember how cool Triton was back in a day! And very pricey!
I had Korg IS40 at that time (early2000’s) and was very happy with it
Surprisingly serum sucks pretty hard, every time I do anything on it, I get lag, then more lag, then even more lag even when my buffer length is maxed and then the reverb won’t even stop when I turn it off and tell my DAW to cut off all sound.