some people find it difficult to get into radiant silvergun and ikaruga because they are a thinking man's game. but i can't think of a company that has had such an audacious debut shooter with little/no experience of programming that style of game before. incredible imagination of what can often be a very stale genre.
The three shooting games they have made have been brilliant, in one way or another. And they always look wonderful.
The team that make the shmups at Treasure are one of the best ever.
I know they are new to the scene, but I have to admit I have become a massive fan of G-Rev and look forward to their software more than Cave and treasure at this point of time.
I don't have a single favorite...I like Toaplan, and increasingly Konami and Seibu. A bit less for Data East, Compile, and manic shmup makers (manics in particular aren't for me).
I also like Treasure shooters a lot. More generally, they are one of my favorite developpers, as they create games with new, original ideas, and always very good technically speaking...
I wish they develop new shmups again !