There are a lot of different level hotels in Riga.
As closiest ones we could recommend (any of the following hotels are easily accessable by Bus 22 from an airport):
Radisson Blu Daugava Hotel - Radisson Blu Daugava Hotel | MeetRiga
Wellton Riverside Hotel & SPA - Wellton Riverside SPA Hotel | MeetRiga
Bellevue Park Hotel Rīga - Bellevue Park Hotel Riga | MeetRiga
Ibis Riga Centre Ibis Riga Centre | MeetRiga