Difficult to think of any in the UK where a more conveniently located main station has been closed - I'd say Manchester Central, Glasgow St Enoch, Liverpool Central and Exchange, Edinburgh Princes Street, Sheffield Victoria, Leicester Central were all less well located than the surviving main stations in those cities. Nottingham Victoria might have been slightly better located than Midland. Going down to slightly smaller cities Derby Friargate was closer to central Derby than Derby Midland is, and Peterborough East might have been better sited than North.
There may be others like Stoke where a station better placed for the city was on a branch line so never had the level of service of the less convenient main station.