No, using a cooktop for popcorn is not better than using a microwave. Most popcorn bags are designed to be heated up in the microwave since  they use microwave radiation to excite water molecules, a process that produces heat. This excitatory process causes the popcorn kernels to expand — thereby producing popcorn
Cooktops don't use microwaves and work by applying heat energy to whatever is being cooked. While cooktop popcorn devices are sold, they don't produce better results compared to cooktops.