AI image generators have split into clear lanes. Midjourney still wins on out-of-the-box aesthetic. DALL-E and Google Imagen lead on following your prompt literally. Flux and Stable Diffusion are where developers and tinkerers go for realism and control. Ideogram owns the one job the others fail at: legible text inside images. Adobe Firefly is the commercially-safe pick for brand work.
The honest reality in 2026: there is no single best image generator, only the best one for your specific job. Pick by what you are making (mood vs exact layout vs text vs commercial-safe), not by which model topped a benchmark this month. Costs run from completely free (Stable Diffusion, Gemini/Imagen) to around $10-$30 a month for the polished apps, or per-image on the API models.
A note that applies to all of them: the model matters less than the prompt. A vague prompt gets a generic image from even the best model. Specify subject, style, lighting, composition, and aspect ratio, and any of these tools improves dramatically.