What are my options to replace this window?
The window frame shown in the picture looks like it would clean-up, paint, and trim-out to leave a clean finished appearance. I'm guessing that the existing window opens and the lever, at the top-center of the window, is for locking the window closed. If that's the case, the window design is allowing for light and for controlled ventilation in a very small opening.
If the window shown in the picture is the metal, hinged, swing-out opener that I'm familiar with, I know that they are expensive and a desirable solution for small basement window openings. The metal components can be much narrower than wood or vinyl window frame components, maximizing the basement's small wall opening for light and air.

I wouldn't advise sealing-up the basement window/vent openings with glass block or any other material. Ventilation can be important for a basement.

If the existing windows are simply a no-go, reach outside of the local big-box home supply store. A handful of 800 calls will give you a good idea whats available in custom order. If you have a non-typical design in mind, talk with some local tradesmen.