C4 was the first pre-workout I tried using and I was relatively unimpressed by it. The marketing behind cellucor is top notch though so it gets pushed pretty hard.
The ones I've been most happy with were Dr. Hyde and GAT Nitraflex. I've also tried the Optimum Nutrition Platinum, the Arnold Iron Pump, and MP Assault.
To answer your question though, a preworkout is usually designed to do a few things:
1. Energy boost (caffeine typically with some other things mixed in)
2. Blood Flow (NO blends to improve vascularity and blood flow)
3. Strength (creatine blends)
There is no doubt that creatine is the single most useful thing out of all of the above, but most people recommend it post-workout, and the creatine in the preworkouts is usually not enough anyways (5g recommended). Energy you can get through a caffeine pill or another source. Vascularity, while impressive looking during your workout, is questionably useful from what I've read.
I'm about to cycle off pre-workout for a month (I've been constant with different preworkouts for quite a few months now) and then may look into blending my own using pure caffeine, beta alanine, BCAAs, etc. after some of my own research.