In terms of pure pace, I believe Frijns, Wickens, Magnussen, da Costa, Nasr, Vietoris, and Bird all deserve to be in F1 one day. Vandoorne and Stevens need more time in an F1 car before they step up, but I think in terms of speed they should be among the 22 (or 26, according to OP) drivers of the future F1 grid. Furthermore, Valsecchi and Razia should receive the opportunity to race in at least one grand prix, although I don’t rate these two as highly as the other drivers I’ve mentioned.
Last year, I was very impressed by James Calado in GP2, although his performance has been mixed this year. I’m still not sold on him, but I think he has the potential. Sirotkin also has a lot of potential, but I have doubts about his readiness for F1. Like Gutierrez, he’s quick, somewhat rough around the edges, and too immature for F1 (at least at the moment) in my opinion.
Glock, Kovalainen, Kobayashi, and Alguersuari are all F1 have-beens. They had their time in F1; now it is time for the next generation of F1 drivers to succeed them.