Yeah I've played Serious Sam, legendary and painkiller. They were good games but very focused on being more arcadey than traditional shooters by speeding up the gameplay's pace and involving only over the top weapons. The level design was a little different to the traditional shooters corridor approach, it was more of an open field which opened up to another open field on defeat of x amount of enemies.

The feeling of the first traditional games, doom, quake (thankyou quake, for without you the A7 engine would not be here! lol), unreal and duke do have that 'unmatched' feeling to them, I think that feeling has something to do with the fact that back in those days games were made 'just for fun' and the ideas were fresh along with the talent excited about experimenting in the new media. The closest I get to the feeling I get playing the original fps's would be in half life 2 and following episodes, I don't think valve have lost track of the formula they used for half life and the dynamic of their company. Each of their games use the same formula and design but each one comes out feeling fresh.

When I think about whether there is still a market for traditional fps gameplay, i think the audience never left, but a lot of new players came in wanting a different experience which retains elements from the first person shooter era but the players tended to lean more on graphics and feature lists over gameplay and good level design, which is why many traditional fps's have been adapted and substantially different to their predecessors (doom 3) or labelled as stale and uninnovative for not adapting to the new age (sin episodes). Valve are the only ones still going strong that I can think of..

EDIT: lol, I do sound like an oldie when I re-read this