Foster retired from international football 18 months ago and has refused to budge from that stance.
But the former Manchester United player has maintained his high standards and produced another superb display in Sunday's 1-1 draw at Aston Villa in front of England manager Roy Hodgson.
Long, who scored the opening goal at Villa Park, said: "Ben is a brilliant keeper. He shows it in training sessions and you can see it every game on the pitch.
Asked if Foster is as good as Manchester City and England number one Hart, Long replied: "I think so. I've never trained with Joe Hart but you see it every day in training, the saves Ben comes out with.
"He is one of the best keepers in England and it is big loss to England not to have him in the ranks but they are lucky to have Hart, who is there to do a job.
"You will have to ask Ben what his reasons are (for not playing for England) but it is working well for him in our team.
"He gets his rest in the international breaks and comes back fresh and puts in performances week in and week out. England's loss is our gain."
Long is full of praise for the way new Baggies boss Steve Clarke has added a passing style to their game alongside the 'difficult to beat' mentality installed during Hodgson's reign as Albion boss.
The Republic of Ireland international said: "He has brought his own stamp on our football. Straight from the start it was all about passing football, and how he wants us to play.
"When he has an idea, he is able to put it across really well to the players.
"He has installed a bit of confidence in the lads to receive the ball in any situation and we are dealing with it pretty well.
"It is nice what you do in training every day comes onto the pitch on a Saturday and that has been the case so far this season.
"It's enjoyable times at West Brom - good football to watch, good to play in and we are getting results at the end of it as well."
Albion have collected 11 points from their opening six games to lie sixth in the Premier League.
Long, whose goal was cancelled out by Darren Bent's equaliser, said: "It shows how far we have come as a team, to come to Villa Park in a big derby and leave disappointed with one point.
"It's good for us a team to expect more from ourselves.
"If we put in performances like that for the rest of the season, we will go very far."
Long is content to adopt the role as the lone striker in a 4-2-3-1 formation.
He said: "It is hard work on your own but we do play football. It means there are not many balls launched up to six feet tall centre-halves to come climbing over the top of me!
"James Morrison keeps threading those balls through and I thought he should have got man of the match at Villa. He was brilliant at picking people out."
Clarke will check on the fitness of skipper Chris Brunt (hamstring) and defender Billy Jones (knee) in the next 24 hours after both were substituted during the first half against Villa.