I voted Bitmap Brothers.
I'll concede that technically they are not as proficient as Team 17 (although, I don't believe Team 17 were quite as proficient as some people remember), but its all about the style and gameplay.
Graphically, I loved the Bitmap Brothers style of graphics, achieving quite nice images with only 16 colours for the early games.
I hated Xenon 2 with a passion. Way too hard, but graphically and sonically, it excelled (at the time).
Speedball, Speedball 2, Cadaver, Chaos Engine, Z, and the big one..... GODS!!!
I hated Magic Pockets first time around, but after cracking it for WHDLoad, I playtested it, and found myself grudgingly quite liking it.
The Bitmaps said the reason why their games only ran in 25 frames was because they didn't want any slowdowns. Personally, I think thats a load of crap, technically, they were rubbish, but, for the most part, the playability of their games and their style negated their inability to actually scroll smoothly!
I liked some of Sensibles games, certainly Mega-lo-Mania was a great title, I couldn't care less about football games (even having written one).
Team 17..... promised so much, and only partially delivered. Agreed Superfrog showed lots of other software companies how to do a fast moving, smooth platform game, even though it had the graphics look of a Codemasters budget title.
Alien Breed was ok, although in reality, it was Miami Chase with different graphics!
Project-X..... never liked that one. Overscan and nice graphics don't make a great game, and I note with humoured interest that for all their slagging off of other developers, all the stuff in Project X apart from the scrolling was 25 frames!
Didn't mind Worms, and Kudos for Team 17 having the foresight to recognise the game, but to be honest, most of the game was done and then presented to them.
I have fonder memories of Bitmap Brothers, I still rate even some of their older titles.
Bitmap Brothers gets my vote.