Which Glock 21 did you try? I could never get into the 3rd gen Glocks... even the SF... but the Gen 4 Glock 21 feels perfect to me. I love it.
Other than that, the XD 45 has a pretty comfortable grip. XDM 45 is worth checking out. The FN 45 is a great option as well...
The Gen4 Glock 21 is definitely my choice though... and I say that having bought and sold an original Gen3 and a Gen 3 SF Glock 21...
I've had the Gen 4 for a year now and have a couple thousand rounds through it. Absolutely great gun... soft shooting too.
Glock 19 G4 BFG | Glock 17 G4 FDE | S&W M&P 22 | S&W M&P 45 | S&W M&P Shield 9 | Ruger GP100 4" | Sig P226 MK25 | Sig P229 Extreme | Sig P320F | Sig P320C | HK USP 9 | HK USP 45 (Tan) | Walther PPQ 9
Daniel Defense DDM4 V4 | Arsenal SGL 21 | ASA SBR | Savage Mark II FV-SR
Mossberg 590A1 20" SP | Mossberg 500 Cruiser